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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Assertion : For real objects, image formed by a convex mirror always lies between pole and focus. Reason : When object moves from pole to infinity, its image will move from pole to focus.A. (a) If both Assertion and Reason are true and the Reason is correct explanation of the Assertion.B. (b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.C. (c) If Assertion is true, but the Reason is false.D. (d) If Assertion is false but the Reason is true. |
| Answer» Correct Answer - A::B | |
| 2. |
In order to obtain a magnification of, `-0.6` (minus 0.6 ) with a concave mirror, the object must be placed :A. at the focusB. between pole and focusC. between focus and centre of curvatureD. beyound the centre of curvature |
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Answer» Correct Answer - A (d) |
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| 3. |
In order to obtain a magnification of, -1.5 with a concave mirror of focal length 16 cm, the object will have to be placed at a distance :A. between 6 cm and 16 cmB. between 23 cm and 16 cmC. between 48 cm and 32 cmD. beyound 64 cm |
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Answer» Correct Answer - A (b) |
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| 4. |
When an object lies at the focus of a concave mirror, them the position of the image formed and its magnification areA. pole and unityB. infinity and unityC. infinity and infintyD. centre of curvature and unity |
| Answer» Correct Answer - C | |
| 5. |
Assertion : If magnification of real object is -2. Then, it is definitely a concave mirror. Reason : Only concave mirror can make real images of real objects.A. (a) If both Assertion and Reason are true and the Reason is correct explanation of the Assertion.B. (b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.C. (c) If Assertion is true, but the Reason is false.D. (d) If Assertion is false but the Reason is true. |
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Answer» Correct Answer - A::B m=-2, means image is real invereted an 2 times magnified. |
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| 6. |
The number of images formed by two plane mirrors inclined at `60^@` of an object placed symmetrically between mirror isA. 6B. 7C. 5D. infinite |
| Answer» Correct Answer - C | |
| 7. |
A point object is placed at equal distance 3 f in front of a concave mirror, a convex mirror and plane mirror separately (event-1). Now, the distance is decreased to 1.5 f from all the three mirror (event-2). Magnitude of focal length of convex mirror and concave mirror is f . Then choose the correct options.A. Maximum distance of object in event-1 from the mirror is from plane mirrorB. Minimum distanc of object in event-1 from the mirrro is from convex mirror.C. Maximum distance of object in event-2 from the mirror is from concave mirrorD. Minimum distance of object in event-2 from the mirror is from plane mirrror |
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Answer» Correct Answer - A In event-1 for concave mirror, `1/v+1/(-3f)=1/(-f)` `:. v=-1.5f` for convex mirror `1/v+1/(-3f)=1/(+f)` `:. v=(3/4)f=-0.75f` for plane mirror, `v = +3f` In event-2 For concave mirror, `1/v+1/(-1.5f)=1/(-f)` `:. v=-3f` for convex mirror `1/v+1/(-1.5f)=1/+f)` `:. v=(3f)/(5)=-0.6f` for plane mirror, `v = +1.5f`. |
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| 8. |
A ball swings back and forth in front of a concave mirror. The motion of the ball is described approximately by the equation `x= f cos (omega)t`, where f is the focal length of the mirror and x is measured along the axis of mirror. The origin is taken at the centre of curvature of the mirror. (a) Derive an expression for the distance from the mirror of the image of the swinging ball. (b) At what point does the ball appear to coincide with its image? (c) What will be the lateral magnifiaction of the image of the ball at time `t= T/2`, where T is time period of oscillation? |
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Answer» Correct Answer - A::B::C::D A(a) At` t=t`, ` u=-(2f+x)` `=-(2f+f cos (omega)t)` Using the mirror formula, `1/v+1/u=1/f` We have, `(1/v) -(1)/(2f+f cos (omega)t) =(-1)/(f)` `:. v=-((2+cos(omega)t)/(1+cos(omega)t))f` i.e distance of image from mirror at time t is `((2+cos(omega)t)/(1+cos(omega)t))f` (b) Ball coincides with its image at centre of curvature, i.e. at x=0 (c) At `t=T//2` or, `(omega)t=(pi), x=-f` i.e. `u=-f` or ball is at focus. so its image is at `(prop)` `m=(prop)`. |
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| 9. |
Prove that for any value of angle i, rays `1 and 2` are parallel |
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Answer» PQ and MN are mutually parallel . Rays 1 and 2 are making equal angles`(=/_i)` from PQ and MN. So, they are muttually parallel. Important result -two plane mirror kept at `90^(@)` deviate each ray of light by `180^(@)` from its orignal path. |
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| 10. |
Two plane mirrors A and B are aligned parallel to each other as shown in the figure. A light ray is incident at an angle of `30^(@)` at a point just inside one end of A. The number of times the ray undergoes reflections (including the first one) before it emerges out is A. `29`B. `30`C. `31`D. `32` |
| Answer» Correct Answer - C | |
| 11. |
A concave mirror of focal length `f` produces a real image `n` times the size of the object. What is the distance of the object from the mirror? |
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Answer» Since image is real, magnification `m` is `-ve`. Let distance of object from pole is `x`. `u=-x,m=-n,f=-f` `m=-(v)/(u)implies-n=(v)/(-x)` `v=-nx` `(1)/(v)+(1)/(u)=(1)/(f)` `(1)/(-nx)+(1)/(-x)=(1)/(-f)implies(1)/(nx)+(1)/(x)=(1)/(f)` `(1+n)/(nx)=(1)/(f)impliesx=((n+1)f)/(n)` |
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| 12. |
A concave mirror has a radius of curvature of 24 cm. How far is an object from the mirror if an image is formed that is: (a) virtual and 3.0 times the size of the object, (b) real and 3.0 times the size of the object and (c) real and `1//3` the size of the object?. |
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Answer» Correct Answer - A::B::C::D Given ,`R=-24 cm` (concave mirror) Hence , `f=(R/2)=-12cm` (a) Image is virtual and 3 times larger, u is nagative and v is positive. Simultaneously ,`|v|=3|u}`.So, let, `u=-x` then `v=+3x` Substituting in the mirror formula, ` 1/v+1/u=1/f` We have, ` 1/(3x)-1/x=1/(-12)` `:. x=8cm.` Therefor , object distance is 8 cm. (b) Image is real and three times larger. Hence, u and v both are negative and `|v|=3|u|.` so let, ` u=-x` then `v=-3x` Substituting in mirror formula ,we have `(1/(-3x))+1/x=-(1)/(12)` or `x=16cm` `:.` Object distance should be 10cm. (c ) Image is real and (1/3)rd the size of object. Hence ,both u and v are negative and `|v|=(|u|)/(3).` So let , u=-x then `v=-(x/3)` Substituting in the formula, we have ` -(3/x)-(1/x)=-(1/12)` ` :. x=48 cm` `:.` Object distance should be `48cm`. |
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| 13. |
A concave mirror of focal length `f` produces a real image `n` times the size of the object. The distance of the object from the mirror isA. `(n-1)f`B. `(n+1)f`C. `(n+1)/(n)f`D. `(n-1)/(n)f` |
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Answer» Correct Answer - C Since image is real and inverted `m=-n` let `u=-x` `m=(v)/(u)implies-n=-(v)/(-x)` `v=-nx` `(1)/(v)+(1)/(u)=(1)/(f)` `(1)/(-nx)+(1)/(-x)=(1)/(-f)implies(1+n)/(nx)=(1)/(f)` `x=((n+1)/(n))f` |
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| 14. |
How far should an object be from a concave spherical mirror of radius 36 cm to form a real image one-ninth its size? |
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Answer» Correct Answer - A::C `f=(R/2)=-18 cm` let `u=-x cm` Then , `v=-(x/9) cm` for real image of `(1/9)th` size.` Using `1/v+1/U=1/f` We have `(1)/(-x//9)+(1)/(-x)=(1)/(-18)` solving we get , `x=180cm.` |
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| 15. |
The focal length of a spherical mirror of radius of curvature 30 cm is:A. 10 cmB. 15 cmC. 20 cmD. 30 cm |
| Answer» Correct Answer - B | |
| 16. |
The mirror used by a dentist to examine the teeth of a person is :A. convexB. concaveC. planeD. any one of the above |
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Answer» Correct Answer - b (b) |
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| 17. |
A point source of light is placed in front of a plane mirror.A. All the reflected rays meet at a point when produced backwardB. Only the reflected rays close to the normal meet at a point when produced backwardC. Only the reflected rays marking a small angle with the mirror, meet at a point when produced backwardD. Light of different colours make different images. |
| Answer» Correct Answer - A | |
| 18. |
The diagrams show the apperance of a fork when placed in front of and closed to two mirrors A and B, turn by turn. (a) Which mirror is convex ? (b) Which mirror is concave ? Give reasons for your choice. |
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Answer» Correct Answer - A (a) Mirror B is convex , It forms a smaller image of frok (b) Mirror A is concave: It forms a larger image of fork |
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| 19. |
Whatever be the position of the object, the image formed by a mirror is virtual, erect and smaller than the object. The mirror them must be :A. planeB. convcaveC. convexD. either concave or convex |
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Answer» Correct Answer - c ( c) |
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| 20. |
A boy is standing in front of and close to a special mirror. He finde the image of his head bigger than normal, the middle part of his body of the same siza, and his legs smaller than normal. The spacial mirror is made up of three types of mirrors in the following order from top downwards:A. Convex, Plane, ConcaveB. Plane, Convex, ConcaveC. Concave, Plane, ConvexD. Convex, Concave, Plane |
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Answer» Correct Answer - A ( c) |
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| 21. |
A small plane mirror placed at the centre of a spherical screen of radius R. A beam of light is falling on the mirror, If the mirror makes `n` revolution per second, the speed of light on the screen after reflection from the mirror will beA. `4pinR`B. `2pinR`C. `(nR)/(2pi)`D. `(nR)/(4pi)` |
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Answer» Correct Answer - A If mirror is turned by `theta`, reflected ray turned by `2theta` `omega=2pin,2omega=4pin` `v=R.2omega=4pinR` |
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| 22. |
The mirror which can form a magnified image of an object is :A. convex mirrorB. plane mirrorC. convace mirrorD. both vonvex and voncave mirrors |
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Answer» Correct Answer - A ( c) |
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| 23. |
Consider two statements A and B given below : A : real image is always inverted B : virtual image is always erect Out of these two statements :A. only A is tureB. only B is trueC. both A and B are trueD. none is true |
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Answer» Correct Answer - A ( c) |
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| 24. |
For what position of an object, a concave mirror forms a real image equal in size to the object?A. convexB. concaveC. planeD. either concave or concave |
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Answer» Correct Answer - A (b) |
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| 25. |
A concave mirror forms the image of an object on a screen. If the lower half of the mirror is covered with an opaque card, the effect would beA. to make the image less brightB. to make the lower half of the imageC. to make the upper half of the image disappear.D. to make the image blurred |
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Answer» Correct Answer - A The complete image is formed but intensity of image will decrease. intensity`prop`(area of mirror reflecting the light). |
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| 26. |
An elevator at rest which is at 10th floor of a building is having a plane mirror fixed to its floor. A particle is projected with a speed `(sqrt(2))m//s` and at `45^(@)` with the horizontal as shown in the figure. At the very instant of projection, the cable of the elevator breaks and the elevator starts falling freely. what will be the separation between the particles and is image 0.5 s after the instant of projection? A. `0.5 m`B. `1 m`C. `2 m`D. `1.5 m` |
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Answer» Correct Answer - B `u_(y)=sqrt(2) sin 45^(@)=1m//s` In vertical direction, `s_(1)=`displacement of partical `=(1)(0.5)-(1/2)(g t)^(2)=0.5-(1/2) (g t)^(2)` `s_(2)` =displacement of mirror `=-(1/2)g t^(2)` `:.` Vertical distance of partical from nirror, `s=s_(1)-s_(2)=0.5 m` Hence, distance between particle and its image `=25=1 m`. |
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| 27. |
Two bigmirrors A and B are fitted side by side on a wall. A man is standing at such a distance from the wall that he can see the erect image of his face in both the mirrors. When the man starts walking towards the mirrors, he finds that size of his face in mirror A goes on increasing but that in mirror B renaubs the same.A. mirror A is concave and mirror B is convexB. mirror A is plane and mirror B is concaveC. mirror A is concave and mirror B is planeD. mirror A is convex and mirror B is concave |
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Answer» Correct Answer - A (c ) |
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| 28. |
Two blocks each of mass m lie on a smooth table. They are attached to two other masses as shown in the figure. The pulleys and strings are light. An object O is kept at rest on the table. The sides AB & CD of the two blocks are made reflecting. The acceleration of two images formed in those two reflecting surfaces w.r.t. each other is: A. `(5g)/(6)`B. `(5g)/(3)`C. `(17g)/(12)`D. `(17g)/(6)` |
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Answer» Correct Answer - D `a_(LHS)=a_(1)=("Net pulling force")/("Total mass")=(3mg)/(4m)=3/4 g` `a_(I_(1))=2a(I_(1)) =3/2 g` `a_(RHS)=a_(2)=("Net pulling force")/("Total mass")=(2mg)/(3m)` `a_(I_(2))=2a(I_(2)) =4/3 g=2/3 g` The relative acceleration is therfore: `(3/2)g+(4/3) g=(17/6)g`. |
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| 29. |
A plane mirror `(M_1)` and a concave mirror `(M_2)` of focal length 10 cm are arranged as shown in figure. An object is kept at origin. Answers the following questions. (consider image formed by single reflection in all cases). If concave mirror is replaced by convex mirror of same focal length then coordinates of image formed by `(M_2)` will beA. `(10 cm, 12 cm)`B. `(10 cm, 22 cm)`C. `(10 cm, 8 cm)`D. None of these |
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Answer» Correct Answer - D `1/v+1/(-20)=1/(+10)` `:. V=+(20/3)cm` `m=-(v/u)=-((+20//3))/((-20))=+(1/3)` `:. I=10(1/3)=10/3 cm` `x=10-(10/3)=(20/3)cm` and `y=20+(20/3)=(80/3) cm`. |
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| 30. |
A plane mirror `(M_1)` and a concave mirror `(M_2)` of focal length 10 cm are arranged as shown in figure. An object is kept at origin. Answers the following questions. (consider image formed by single reflection in all cases). The coordination of image formed by concave mirror areA. `(10 cm, -40 cm)`B. `(10 cm, -60 cm)`C. `(10 cm, 8 cm)`D. None of these |
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Answer» Correct Answer - D Object is placed at centre at curvature of mirror. Hence, image is at the same point, real, inverted and of same size. Hence, coordinates are `(20cm, 0)`. |
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| 31. |
For a concave mirror the magnificant of a real image was found to be twice as greater when the object was 15 cm from the mirror as it was when the object was 20 cm from the mirror. The focal length mirror isA. 5.0 cmB. 7.5 cmC. 10 cmD. 12.5 cm |
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Answer» Correct Answer - C When object is at distance 15 cm, magnification is `2lamda` when object is at distance 20 cm, magnification is `lamda` `m_1=-lamda,u_1=-20cm` `m=-(v)/(u)implies-lamda=-(v_1)/(-20)` `v_1=-20lamda` `m_2=-2lamda,u_2=-15cm` `m=-(v)/(u)implies-2lamda=-(v_2)/(-15)` `v_2=-30lamda` `(1)/(f)=(1)/(v_2)+(1)/(u_2)=(1)/(v_1)+(1)/(u_1)` `(1)/(-30lamda)+(1)/(-15)=(1)/(-20lamda)+(1)/(-20)` `(1)/(20lamda)-(1)/(30lamda)=-(1)/(20)+(1)/(15)` `(1)/(60lamda)=(-3+4)/(60)implieslamda=1` `(1)/(f)=(1)/(v_2)+(1)/(u_2)=(1)/(-30lamda)+(1)/(-15)` `=(1)/(-30)+(1)/(-15)=(-(1+2))/(30)` `f=-10cm` |
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| 32. |
A diverging mirror is :A. a plane mirrorB. a convex mirrorC. a convace mirrorD. a shaving mirror |
| Answer» Correct Answer - B | |
| 33. |
In a convex spherical mirror, reflection of light takes place at :A. a flat surfaceB. a bent-in surfaceC. a bulging-out surfaceD. an uneven surface |
| Answer» Correct Answer - C | |
| 34. |
The firld of view is maximum forA. plane mirrorB. concave mirrorC. convex mirrorD. cylindrical mirror |
| Answer» Correct Answer - C | |
| 35. |
In the concave reflector of a torch, the bulb is placed :A. between the pole and focus of reflectorB. at the focus of reflectorC. between focus and centre of curvature of reflectorD. at the cetre of curvature of reflector |
| Answer» Correct Answer - B | |
| 36. |
Assertion : Two plane mirrors kept at right angles deviate any ray of light by `180^@` after two reflection. Reason : The above condition is satisfied only for angle of incidence `i=45^@`.A. (a) If both Assertion and Reason are true and the Reason is correct explanation of the Assertion.B. (b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.C. (c) If Assertion is true, but the Reason is false.D. (d) If Assertion is false but the Reason is true. |
| Answer» Correct Answer - C | |
| 37. |
An object is placed in from of a convex mirror of focal length 50 cm, if the image is one fourth the size of the object, the distance of the image from the mirror isA. 25 cmB. 37.5 cmC. 50 cmD. 75 cm |
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Answer» Correct Answer - B `u=-x,m=(1)/(4)` `m=-(v)/(u)implies(1)/(4)=-(v)/(-u)` `v=(x)/(4)` `(1)/(v)+(1)/(u)=(1)/(f)implies(1)/((x)/(4))+(1)/(-x)=(1)/(50)` `(3)/(x)=(1)/(50)` `x=150cm,v=(x)/(4)=(150)/(4)=37.5cm` |
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| 38. |
An obejct is placed at a distance `2f` from the pole of a convex mirror of focal length `f`. The linear magnification isA. `(1)/(3)`B. `(2)/(3)`C. `(3)/(4)`D. 1 |
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Answer» Correct Answer - C `(1)/(3)+(1)/(-2f)=(1)/(f)implies(1)/(v)=(1)/(f)+(1)/(2f)=(3)/(2f)` `v=(3f)/(2)` `m=-(v)/(u)-((3f)/(2))/(2f)=(3)/(4)` |
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| 39. |
Magnitude of focal length of a spherical mirror is f and magnitude of linear magnification is `1/2`A. If image is inverted, it is a concave mirrorB. If image is erect, it is a convex mirrorC. Object distance from the mirror may be `3 f`D. Object distance from the mirror may be f. |
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Answer» Correct Answer - A::B::C::D Inverted and real image is formed by concave mirror. Let `u= -x` , then `v= +(x/2)` `:. (1)/(+x//2) +(1)/(-x)=(1)/(+f)` `:.x=3f` Erect and virtual image is formed by convex mirror. let `u=-x`, then `v= +(x/2)` `(1/(-x//2))+(1)/(-x)=(1)/(+f)` `x= +f`. |
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| 40. |
A spherical mirror and a thin spherical lens have each a focal length of `- 15 cm`. The mirror and lens are likely to beA. both concaveB. both convexC. the mirror is concave and the lens is convexD. the mirror is convex but the lens is concave |
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Answer» Correct Answer - A both concave. |
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| 41. |
Where should an object be placed in front of a convex lens to get a real to get real image of the size of the object ?A. at the principalB. at twice the focal lengthC. at infinityD. between the optical centre of the lens its principal focus |
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Answer» Correct Answer - A at twice the focal length |
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| 42. |
A plane mirror is lying in x-y plane .Object velocity is ` V_0=(2 hati-3 hatj+4 hatk) m//s`. Find the image velocity. |
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Answer» Correct Answer - A::B::C::D Components of object velocity parallel to plane mirror (or lying in x-y palne )remain unchanged.But component perpendicular to plane mirror chamges its direction but magnitude remains the same.Hence ,the image velocity is ` v_(1)=(2 hat i-3 hat j-4 hat k)m//s` |
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| 43. |
A plane mirror `(M_1)` and a concave mirror `(M_2)` of focal length 10 cm are arranged as shown in figure. An object is kept at origin. Answers the following questions. (consider image formed by single reflection in all cases). if concove mirror is replaced by another plane mirror parallel to x-axis, then coordinates of image formed by `(M_2)` areA. `(40 cm, 20 cm)`B. `(20 cm, 40 cm)`C. `(-20 cm, 20 cm)`D. None of these |
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Answer» Correct Answer - D Plane mirror forms at equal distance on opposite sides Hence, `x=0, y=40 cm`. |
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| 44. |
An object is moving towards a concave mirror of focal length 24 cm. When it is at a distance of 60 cm from the mirror, its speed is `9 cm//s`. The speed of its image at that instant , isA. `4 cm//s` towards the mirrorB. `6 cm//s` towards the mirrorC. `4 cm//s`away from the mirrorD. `6 cm//s`away from the mirror |
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Answer» Correct Answer - C `1/v+1/(-60)=(1/-24)` `:. V= -40 cm` `m=-(v/u)= -((40)/(-60))=(-2)/(3)` Image speed is `m^(2)`-times the object speed and opposite to the direction of object velocity. |
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| 45. |
A point object is placed on the principal axis of a concave mirror of focal length 20 cm. At this instant object is given a velocity v towards the axis (event-I) or perpendicular to axis (event-2). Then, speed of image A. In event-1 is 2vB. In event-1 is 4vC. In event-2 is 2vD. In event-2 is 4v |
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Answer» Correct Answer - A::B::C `1/v+1/(-30)=(1/(-20)` Solving we get, `v= -60 cm` `m=(v)/(u)=-((-60))/((-30))=-2` Speed of image (in event-1) is `m^(2)` times and m times in event-2. |
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| 46. |
The image of an object placed on the principal axis of a concave mirror of focal length 12 cm is formed at a point which is 10cm more distance form the mirror than the object. The magnification of the image isA. 1.5B. 2C. 2.5D. 3 |
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Answer» Correct Answer - A `u=-x,v=-(10+x),f=-12` `(1)/(v)+(1)/(u)=(1)/(f)implies(1)/(-(10+x))+(1)/(-x)=(1)/(-12)` `(x+10+x)/((10+x)x)=(1)/(12)` `24x+120=x^2+10x` `x^2-14x-120=0` `(x-20)(x+6)=0` `x=20cm` `u=-20cm`, `v=-(10+20)=-30cm` `m=-(v)/(u)=-(-30)/(-20)=(3)/(2)=1.5` |
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| 47. |
Assume that a certain spherical mirror has a focal length of -10.0 cm. Locate and describe the image for object distances of (a) 25.0 cm (b) 10.0 cm (c) 5.0 cm. |
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Answer» Correct Answer - A::B::C Apply `1/v+1/u=1/f` (a) `f=-10cm, u=-25cm` Solving ,we get `v=-16.7 cm` Since, v is negative , image is in front of mirror .So, it is real, Similarly, we can solve for other parts. |
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| 48. |
The angle of incidence for a ray of light passing throught the centre of curvature of a concave mirror is :A. `45^(@)`B. `90^(@)`C. `0^(@)`D. `180^(@)` |
| Answer» Correct Answer - C | |
| 49. |
A ray of light falls on a plane mirror. When the mirror is turned, about an axis at right angles to the plane of mirror by `20^(@)` the angle between the incident ray and new reflected ray is `45^(@)`. The angle between the incident ray and original reflected ray was therefore.A. `35^ (@)` or `50^ (@)`B. `25^(@)` or `65^(@)`C. `45^(@)` or `5^(@)`D. None of these |
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Answer» Correct Answer - D Let i is the angle between incident ray and original reflected ray, Then initial angle between them will be `180^(@)-2i`. When mirror is rotated by `20^(@)` , then reflected ray will rotate by `40^(@)` `:. 180^(@) -2i+- 40^(@) =45^(@)` Solving we get, ` i=47.5^(@) or 87.5^(@)`. |
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| 50. |
A concave mirror has a focal length of 25 cm. At which of the following distace should a person hold his fce from this concave mirror so that it may act as a shaving mirror ? (a) 45 cm (b) 20 cm 25 cm (c ) 25 cm (d) 30 cm Give reason for your choice.A. N/AB. N/AC. N/AD. N/A |
| Answer» Correct Answer - 20 cm | |