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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.
| 401. |
The separation between the screen and a plane mirror is 2 r . An isotropic point source of light is placed exactly midway between the mirror and the screen. Assume that mirror reflects 100% of incident light. Then the ratio of illuminances on the screen with and without the mirror isA. `10 : 1`B. `2 : 1`C. `10 : 9`D. `9 : 1` |
| Answer» Correct Answer - c | |
| 402. |
In a grease spot photometer light from a lamp with dirty chimney is exactly balanced by a point source distance 10 cm from the grease spot. On clearing the chimney, the point source is moved 2 cm to obtain balance again. The percentage of light absorbed by dirty chimney is nearlyA. `56%`B. `44%`C. `36%`D. `64%` |
| Answer» Correct Answer - c | |
| 403. |
Near and far points of a human eye areA. 0 and 25 cmB. 0 and `oo`C. 25 cm and 100 cmD. 25 cm and `oo` |
| Answer» Correct Answer - d | |
| 404. |
Retina of eye acts like ........ of camerA. ShutterB. FilmC. LensD. None of these |
| Answer» Correct Answer - b | |
| 405. |
Two parallel pillars are `11 km` away from an observer. The minimum distance between the pillars so that they can be seen separately will beA. 3.2 mB. 20.8 mC. 91.5 mD. 183 m |
| Answer» Correct Answer - a | |
| 406. |
An object of length 6 cm is placed on the principle axis of a concave mirror of focal length f at a distance of 4 f . The length of the image will beA. 2 cmB. 12 cmC. 4 cmD. 1.2 cm |
| Answer» Correct Answer - a | |
| 407. |
Image formed by a concave mirror of focal length 6 cm , is 3 times of the object, then the distance of object from mirror isA. `-4 cm`B. `8 cm`C. `6 cm`D. `12 cm` |
| Answer» Correct Answer - a | |
| 408. |
Convergence of concave mirror can be decreased by dipping inA. WaterB. OilC. BothD. None of these |
| Answer» Correct Answer - d | |
| 409. |
What will be the height of image when an object of 2 mm is placed on the axis of a convex mirror at a distance 20 cm of radius of curvature 40 cmA. 20 mmB. 10 mmC. 6 mmD. 1 mm |
| Answer» Correct Answer - d | |
| 410. |
Can the relative refractive index of a medium w.r.t. another medium be less than unity ? |
| Answer» Yes, for example, the relative refraction index of water w.r.t. glass `= (4//3)/(3//2) = (8)/(9) lt 1`. | |
| 411. |
Can the absolute value of refractive index of a medium be less than unity ? |
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Answer» No, this is because absolute refractive index `mu = ( c)/(v) = ("speed of light in vacuum")/("speed of light in medium")` and `v` is always less than `c`. |
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| 412. |
The plano-convex lens of focal length `20cm` and `30cm` are placed together to form a double convex lens. The final length will beA. `12cm`B. `60cm`C. `20cm`D. `30cm` |
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Answer» (a) Equivalent focal length `1/F=1/(f_(1))+1/(f_(2))=1/20+1/30` `F=(20xx30)/(20+30)=600/50=12cm` |
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| 413. |
An object is placed at a distance `20cm` from the pole of a convex miror of focal length `20cm`. The image is produced aA. `13.3cm`B. `20cm`C. `25cm`D. `10cm` |
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Answer» (d) `u=-20cm, f=20cm` From mirror formula `1/f=1/v+1/u` `1/20=1/v+1/(-20)` `1/v=1/20+1/20` `1/v=1/20+1/20` `1/v=2/20` `impliesv=10cm` |
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| 414. |
STATEMENT-`1` The power of a thin lens does not depend upon the surrounding medium `STATEMENT 2` power of a thin lensA. STATEMENT -`1`is true statement `2` is true,Statement -`2`is a correct explanation for statement -`1`B. STATEMENT -`1`is true statement `2` is true,Statement -`2`is a not a correct explanation for statement -`1`C. Statement -`1`is true,Statement -`2`is FalseD. Statement -`1`is False ,Statement -`2`is True |
| Answer» Correct Answer - D | |
| 415. |
A bi-convex lens is formed with two thin plano-convex lenses as shown in the figure. Refractive index n of th efirst lens is 1.5 and that of the second lens if 1.2 Both the curved surfaces are of the same radius of curvature `R=14cm. ` For this bi-convex lens, for an object distance of 40cm, the image distance will be A. `.280.0cm`B. `40.0cm`C. `21.5cm`D. `13.3cm` |
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Answer» Correct Answer - B `(1)/(f_(1))=(1.2-1)((1)/(oo)-(1)/(-14))=(0.2)/(14)` `(1)/(f_(2))=(1.5-1)((1)/(14)-(1)/(oo))=(0.5)/(14)` `(1)/(f_(eq))=(0.7)/(1.4)=(1)/(20)` `(1)/(v)-(1)/(-40)=(1)/(20)` `v=40cm` |
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| 416. |
`µ_(1)` and `µ_(2)` are the refractive index of two mediums and `v_(1)` and `v_(2)` are the velocity of light in these in two mediums respectively. Then, the relation connecting these quantities isA. `v_(1)=v_(2)`B. `µ_(2)v_(1)= µ_(1)v_(2)`C. `µ_(1)^(2)v_(1)= µ_(2)^(2)v_(2)`D. `µ_(1)v_(1)= µ_(2)v_(2)` |
| Answer» Correct Answer - D | |
| 417. |
When light is refracted into a mediumA. its wavelength and frequency both increaseB. its wavelength increases but frequency remain unchangedC. its wavelength decreased but frequency remain unchangedD. its wavelength and frequency both decreased |
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Answer» Correct Answer - C (c ) When light is refracted into a medium from vaccum its wavelength decrease but frequency remain unchanged. |
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| 418. |
A spot is placed on the bottom of a slab made of transperent material of refractive index 1.5. The spot is viewed vertically from the top when it seems to be raised by 2 cm. Then, the height of the slab isA. 10 cmB. 8 cmC. 6 cmD. 4 cm |
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Answer» Correct Answer - C (c ) We have, `d_(app)=d/µ` or `(d-2)=d/1.5` `therefore` d=6 cm |
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| 419. |
Resolving power of a microscope is given byA. `(2musintheta)/(lamda^(2))`B. `(musintheta)/(lamda)`C. `(2musintheta)/(lamda)`D. `(2mucostheta)/(lamda)` |
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Answer» Correct Answer - C (c ) Resolving power of microscope is given by,`(2µsintheta)/lambda`. |
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| 420. |
Reflecting telescope consists ofA. convex mirror of large aperatureB. concave mirror of large aperatureC. Concave lens of small aperatureD. None of these |
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Answer» Correct Answer - B (b) Reflecting telescope consist of concave mirror of large aperature. |
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| 421. |
A reflecting telescope utilizesA. A concave mirrorB. A convex mirrorC. A prismD. A plano-convex lens |
| Answer» Correct Answer - a | |
| 422. |
In Gallilean telescope, the final image formed isA. real,erect and enlargedB. virtual,erect and enlargedC. real,inverted and enlargeD. virtual,inverted and enlarged |
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Answer» Correct Answer - A (b) If in an astronomical telescope, the convergent eye-piece is replaced by a divergent lens which is placed in such a way that rays from objective are directed towards its focus, final image will be erect, enlarged and virtual, and hence, it is called Gallilean telescope. |
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| 423. |
Reflecting telescope consists ofA. convex mirror of large apertureB. concave mirror of large apertureC. concave lens of small apertureD. None of the above |
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Answer» Correct Answer - B Reflecting telescope consists of concave mirror of large aperture. |
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| 424. |
Magnifying power of a Galilean telescope is given byA. `f_(o)/(f_(e))(1-f_(e)/D)`B. `f_(o)/(f_(e))(1+f_(e)/D)`C. `f_(o)/(f_(e))(1+(2f_(e))/D)`D. `f_(o)/(f_(e))(1-(2f_(e))/D)` |
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Answer» Correct Answer - A (a) Magnifying power of a Gallilean telescope is given by, `m=f_(o)/(f_(e))(1-f_(e)/D)` |
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| 425. |
If both the object and image are at infinite distances form a refracting telescope its magnifying power will be equal toA. The sum of the focal lengths of the objective and the eyepieceB. The difference of the focal lengths of the two lensesC. The ratio of the focal length of the objective and eyepieceD. The ratio of the focal length of the eyepiece and objective |
| Answer» Correct Answer - c | |
| 426. |
The number of lenses in a terrestrial telescope isA. twoB. threeC. fourD. six |
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Answer» Correct Answer - B (b) In terrestrial telescope, there are three lenses, objective, eye piece and third is erecting lens, it is placed at 2f from intermediate image. |
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| 427. |
Angle of prism is `A` and its one surface is silvered. Light rays falling at an angle of incidence `2 A` on first surface return back through the same path after suffering reflection at second silvered surface. Refraction index of the material of prism is |
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Answer» Given`i=2A` For figurer=`A` `:. mu=(sin i)/(sin r)=(sin 2A)/(sin A)` `=(2 sinAcosA)/(sinA)=2cosA` |
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| 428. |
A man of length h requires a mirror, to see his own complete image of length at least equal toA. `h/4`B. `h/3`C. `h/2`D. `h` |
| Answer» Correct Answer - c | |
| 429. |
Two lenses are placed in contact with each other and the focal length of combination is `80 cm`. If the focal length of one is `20 cm`, then the power of the other will beA. `1.66 D`B. `4.00 D`C. `-1.00 D`D. `-3.75 D` |
| Answer» Correct Answer - d | |
| 430. |
A convex lens of focal length 40 cm is in contact with a concave lens of focal length 25 cm. The power of the combination isA. `-1.5 D`B. `-6.5 D`C. `+6.5 D`D. `+6.67 D` |
| Answer» Correct Answer - a | |
| 431. |
A lens of power `+2` dioptres is placed in contact with a lens of power `-1` dioptre. The combination will behave likeA. A convergent lens of focal length 50 cmB. A divergent lens of focal length 100 cmC. A convergent lens of focal length 100 cmD. A convergent lens of focal length 200 cm |
| Answer» Correct Answer - c | |
| 432. |
Magnification by a lens of an object at distance 10 cm from it is -2. now a seconnd lens is placed exactly at the same positon where first was kept, without changing the distance between object and lens. The magnification by this second lens is -3. What is the focal length of the combination when both lenses are in contact ?A. `60/17 cm `B. `5/17 cm `C. `12/7 cm `D. `13/9 cm ` |
| Answer» Correct Answer - A | |
| 433. |
Magnification by a lens of an object at distance 10 cm from it is -2. now a seconnd lens is placed exactly at the same positon where first was kept, without changing the distance between object and lens. The magnification by this second lens is -3. Now both the lenses are kept in contact at the same place. what will be the new magnification ?A. `-13/5`B. `-12/7`C. `-6/11`D. `-5/7` |
| Answer» Correct Answer - C | |
| 434. |
A lens ( focal length `50 cm` ) forms the image of a distant object which subtends an angle of 2 milliradian at the lens. What is the size of the image ?A. 5 mmB. 1 mmC. 0.5 mmD. 0.1 mm |
| Answer» Correct Answer - c | |
| 435. |
A telescope has an objective of focal length 100 cm and an eye-piece of focal length 5 cm. What is the magnifying power of the telescope when it is in normal adjustment?A. 0.2B. 2C. 20D. 200 |
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Answer» Correct Answer - C (c ) The magnifying power of the telescope in normal adjustment, `m=f_(o)/(f_(e))=100/5=20` |
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| 436. |
When sun light is scatterred by minute particles of atmosphere, then the intensity of light scattered away is proportional toA. `("wavelength of light")^(4)`B. `("frequency of light")^(4)`C. `("wavelength of light")^(2)`D. `("frequency of light")^(2)` |
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Answer» Correct Answer - B (b) molecules of a medium after absorbing incoming light radiations, emit them in all directions. This phenomenen is called scattering. According to scientist Rayleigh, the intensity of scattered light `prop1/lamda^(4)propv^(4)` where, v is the frequency. |
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| 437. |
An observer looks at a tree of height 15 m with a telescope of magnifying power 10. To him, the tree appearsA. 10 times tallerB. 15 times tallerC. 10 times nearerD. 15 times nearer |
| Answer» Correct Answer - c | |
| 438. |
For a telescope to have large resolving power theA. Focal length of its objective should be largeB. Focal length of its eye piece should be largeC. Focal length of its eye piece should be smallD. Aperture of its objective should be large |
| Answer» Correct Answer - d | |
| 439. |
Which is not true for the image formed in a plane mirror ? The image isA. virtualB. erectC. Iaterally invertedD. closer to the mirror than the object. |
| Answer» Correct Answer - D | |
| 440. |
A short linear object of length b lies along the axis of a concave mirror of focal length f at a distanee u from the pole of the mirror. The size of the image is approximately equal toA. `b((mu - f)/(f))^(1//2)`B. `b((f)/(u - f))^(1//2)`C. `b((u - f)/(f))`D. `b((f)/(u - f))` |
| Answer» Correct Answer - D | |
| 441. |
A short linear object of length b lies along the axis of a concave mirror of focal length f at a distanee u from the pole of the mirror. The size of the image is approximately equal toA. `l ((u - f)/(f))^(1//2)`B. `l ((u - f)/(f))^(2)`C. `l ((f)/(u - f))^(1//2)`D. `l ((f)/(u - f))^(2)` |
| Answer» Correct Answer - D | |
| 442. |
A thin rod of length `f//3` is placed along the optical axis of a concave mirror of focal length f such that its image whichis real and elongated just touches the rod. Calculate the magnification.A. `f`B. `(1)/(2) f`C. `2 f`D. `(1)/(4) f` |
| Answer» Correct Answer - B | |
| 443. |
A light ray from air is incident (as shown in figure ) at one end of a glass fiber ( refractive index `mu=1.5)` making an incidence angle of `60^(@)` on the lateral surface, so that it undergoes a total internal reflection. How much time would it take to traverse the straight fiber of length `1 km `? A. 3.3 `mu`sB. 6.6 `mu`sC. 5.7 `mu`sD. 3.85 `mu`s |
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Answer» Correct Answer - D (d) When total internal reflection just takes place from lateral surface, i=C i.e., `60^(@)=C` `rArr sin 60^(@)=sinC= 1/murArrmu=2/sqrt3` Time taken by light to traverse some distance in a medium, `t=(mux)/c=(2/sqrt3xx10^(3))/(3xx10^(8))=3.85mus` |
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| 444. |
A short linear object of length b lies along the axis of a concave mirror or focal length f at a distance u from the pole of the mirror. The size of the image is approximately equal toA. `(f/(u-f))b`B. `(f/(u-f))^(2)b`C. `(f/(u-f))b^(2)`D. `(f/(u-f))` |
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Answer» Correct Answer - B (b) Using mirror formula, `1/v+1/(-u)=1/(-f)` Multiplying with u, `u/v=(-u)/f)+1=(f-u)/f` `therefore` Magnification, m=`v/u=(f/(f-u))` Now, `abs(dv)=m^(2)abs(du)` Sizze of image=`(f/(f-u))^(2)`cdotb` |
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| 445. |
An object is kept at a distance of 16 cm from a thin lens and the image formed is real. If the object is kept at a distance of 6 cm from the same lens, the image formed is virtual. If the size of the image formed are equal, the focal length of the lens will beA. 8 cmB. 5 cmC. 11 cmD. `sqrt(96) cm` |
| Answer» Correct Answer - C | |
| 446. |
An object is kept at a distance of `16 cm` from a thin lens and the image formed is real. If the object is kept at a distance of `6 cm` from the lens, the image formed is virtual. If the sizes of the images formed are equal, the focal length of the lens will beA. 19 cmB. 17 cmC. 21 cmD. 11 cm |
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Answer» Correct Answer - D (d) Lens should be convex. Images should be magnified by focal length 16 cm length should lie between f and 2f. Because corresponding to 6 cm (`gt`f) length image should be magnified. from the given options, if f = 11 cm. Then, 6 cm, `gt` f and 11 cm`gt` 16 cm `gt` 22 cm or f`gt`16 cm `gt` 2f |
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| 447. |
A ray falls on a prism `ABC(AB=BC)` and travels as shown in adjoining figure.The minimum refraction index of the prism material should be -A. 43558B. `sqrt2`C. 1.5D. `sqrt3` |
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Answer» Correct Answer - B (b) Angle I at bothfocus will be `45^(@)`. For TIR to take place, `igttheta_(C) or sinigtsintheta_(C)` `therefore 1/sqrt2gt1/muor mugtsqrt2` |
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| 448. |
A point source of light is placed 4 m below the surface of water of refractive index `(5)/(3).` The minimum diameter of a disc, which should be placed over the source, on the surface of water to cut off light coming out of water isA. 2 mB. 6 mC. 4 mD. 3 m |
| Answer» Correct Answer - b | |
| 449. |
A fist looking from within water sees the outside world through a circular horizon. If the fish `sqrt(7)` cm below the surface of water, what will be the radius of the circular horizonA. 3.0 cmB. 4.0 cmC. 4.5 cmD. 5.0 cm |
| Answer» Correct Answer - a | |
| 450. |
The radius of curvature for a convex lens is 40 cm , for each surface. Its refractive index is 1.5. The focal length will beA. 40 cmB. 20 cmC. 80 cmD. 30 cm |
| Answer» Correct Answer - a | |