InterviewSolution
Saved Bookmarks
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.
| 701. |
A light beam is being reflected by using two mirrors, as in a periscope used in submarines. If one of the mirrors rotates by an angle `theta`, the reflected light will deviate from its original path by the angleA. `2 theta`B. `0^(@)`C. `theta`D. `4 theta` |
| Answer» Correct Answer - a | |
| 702. |
The distance between a convex lens and a plane mirror is 15 cm. The parallel rays incident on the convex lens, after reflection from the mirror, form image at the optical centre of the lens. Draw the ray-diagram and find out the focal length of the lens. |
|
Answer» Correct Answer - 30 cm |
|
| 703. |
The distance between a convex lens and a plane mirror is 10 cm. The parallel rays incident on the convex lens after reflection from the mirror forms image at the potical centre of the lens. Focal length of lens will beA. `10 cms^(-1)`B. 20 cmC. 30 cmD. Cannot be determined |
| Answer» Correct Answer - b | |
| 704. |
Focal length of a thin convex lens is 30 cm. At distance of 10 cm from the lens there is a plan refracting surface of refractive index `3//2`. Where w the parallel rays incident on lens converge ? A. At a distance of 27.5 cm from the lensB. At a distance of 25 cm from the lensC. At a distance of 45 cm from the lensD. At a distance of 40 cm from the lens |
| Answer» Correct Answer - D | |
| 705. |
An equiconvex lens of glass `(mu_(g) = 1.5)` of focal length 10 cm is silvered on one side. It will behave like aA. concave mirror of focal length 10 cmB. convex mirror of focal length 5.0 cmC. concave mirror of focal length 2.5 cmD. convex mirror of focal length 20cm |
| Answer» Correct Answer - C | |
| 706. |
A small telescope has an objective lens of focal length `144 cm` and an eye-piece of focal length `6.0 cm`. What is the magnifying power of the telescope ? What is the separation between the objective and the eye-piece ?A. `0.75 cm`B. `1.38 cm`C. `1.0 m`D. `1.5 m` |
|
Answer» Correct Answer - D The separation between the objective and the eyepiece = Length of the telescope tube `f = f_(0) + f_(e)` Here, `f_(0) = 144 cm, = 1.44 m, f_(e) = 6.0 cm = 0.06 m` `:. F = 1.44 + 0.06 = 1.5 m` |
|
| 707. |
A giant telescope in an observatory has an objective of focal length 19 m and an eye-piece of focal length `1.0 cm`. In normal adjustment, the telescope is used to view the moon. What is the diameter of the image of the moon formed by the objective? The diameter of the moon is `3.5 xx 10^(6)m`. and the radius of the lunar orbit round the earth is `3.8 xx 10^(8) m`.A. `10 cm`B. `12.5 cm`C. `15 cm`D. `17.5 cm` |
|
Answer» Correct Answer - D As `u gt gt f_(0), v = f_(0) = 19 m` Now `u = - 3.8 xx 10^(8) m`. Therefore, magnification porduced by the objective is `m_(0) = (v)/(u) = - (19)/(3.8 xx 10^(8)) = -0.5 xx 10^(-7)` `:.` Diameter fo the image of moon is `3.5 xx 10^(6) xx 0.5 xx 10^(-7) = 0.175 m = 17.5 cm` |
|
| 708. |
In an astronomical telescope in normal adjustment a straight black line of length `L` is drawn on inside part of objective lens. The eye piece forms a real image of this line. The length of this image is `I`. The magnification of the telescope isA. `L/l`B. `L/l+1`C. `L/l-1`D. `(L+l)/(L-l)` |
| Answer» Correct Answer - a | |
| 709. |
In an astronomical telescope in normal adjustment a straight black line of length `L` is drawn on inside part of objective lens. The eye piece forms a real image of this line. The length of this image is `I`. The magnification of the telescope isA. `L/l`B. `L/l + 1`C. `L/l-1`D. `(L + l)/(L -l)` |
|
Answer» Correct Answer - A Let `f_(o)` and `f_(e)` be the focal lengths of the objective and eyepiece respectively. For normal adjustment, distance from the objective to the eyepiece (tube length ) `= f_(o) + f_(e)`. Treating the line of the objective as the object, and the eyepiece as the lens, `u = -(f_(o) + f_(e))` and `f = f_(e)` `:. (1)/(v) = (1)/(f_(e)) -(1)/(f_(o)+f_(e))= (f_(o))/((f_(e)+f_(e))f_(e))` or `v = ((f_(o) + f_(e))f_(e))/(f_(o))` Magnitifcation `= |v/u| = (f_(e))/(f_(o)) = ("image size")/("object size") = (I)/(O)` `:. (f_(o))/(f_(e)) = (L)/(l)` = magnification of telescope in normal adjustment. |
|
| 710. |
A ray of monochromatic light is incident on one refracting face of a prism of angle `75^(@)`. It passes through the prism and is incident on the other face at the critical angle. If the refractive index of the material of the prism is `sqrt2` , the angle of incidence on the first face of the prism isA. `30^(@)`B. `45^(@)`C. `60^(@)`D. `0^(@)` |
| Answer» Correct Answer - b | |
| 711. |
A ray of monochromatic light is incident on one refracting face of a prism of angle `75^(@)`. It passes through the prism and is incident on the other face at the critical angle. If the refractive index of the material of the prism is `sqrt(2)`, the angle of incidence on the first face of the prism is |
|
Answer» `mu=(1)/(sin C)`and`sqrt(2)=(1)/(sin C)` or`sinC=(1)/(sqrt(2))` or `C=45^(@)` now`A=r_(1)+r_(2)=r_(1)+C ( because r_(2)=C)` or`75^(@)=r_(1)+45^(@) :.r_(1)=30^(@)` further`mu=(sin i_1)/(sin r_(1))` or `sin i_(1)=muxxsinr_(1)=sqrt(2)xxsin 30^(@)` or`sin i_(1)=sqrt(2)xx(1)/(2)=(1)/(sqrt(2)) rArri_(1)=45^(@)` |
|
| 712. |
Three immiscibles transparent liquids with erefractive indices 3/2,4/3 and 6/5 are arranged one on top of another. The depth of the liquid are 3 cm, 4 cm and 6 cm respectively. The apparent depth of the vessel isA. 10 cmB. 9 cmC. 8 cmD. 7 cm |
|
Answer» Correct Answer - A (a) As, `d_(app)=d_(1)/(µ_(1))+d_(2)/(µ_(2))+d_(3)/(µ_(3))=3/(3//2)+4/(4//3)+6/(6//5)` =2+3+5=10 cm |
|
| 713. |
Assertion `:` The stars twinkle while the planets do not. Reason `:` The stars are much bigger in size than the planets.A. If both assertion and reason are true and the reason is the correct explanation of the assertionB. If both assertion and reason are true but reason is not the correct explanation of the assertionC. If assertion is true but reason is falseD. If the assertion and reason both are false |
| Answer» Correct Answer - b | |
| 714. |
Assertion `:` Owls can move freely during night. Reason `:` They have large number of rods on their retina.A. If both assertion and reason are true and the reason is the correct explanation of the assertionB. If both assertion and reason are true but reason is not the correct explanation of the assertionC. If assertion is true but reason is falseD. If the assertion and reason both are false |
| Answer» Correct Answer - c | |
| 715. |
We combined a convex lens of focal length `f_(1)` and concave lens of focal lengths `f_(2)` and their combined focal length was F . The combination of these lenses will behave like a concave lens, ifA. `F_(1) gt f_(2)`B. `f_(1) lt f_(2)`C. `f_(1) = f_(2)`D. `f_(1) le f_(2)` |
|
Answer» Correct Answer - A For combinatio of one convex and one concave lens `(1)/(F)=(1)/(f_(1))-(1)/(f_(2))rArr F=(f_(1)f_(2))/(f_(2)-f_(1))` If `f_(1)gt f_(2)`, then F will be negative. |
|
| 716. |
When we see an object the image formed on the retina isA. real and invertedB. virtual and erectC. real and erectD. virtual and inverted |
|
Answer» Correct Answer - A Image formed on the retina is real and inverted. |
|
| 717. |
For the myopic eye, the defect is cured byA. Convex lensB. Concave lensC. Cylindrical lensD. Toric lens |
| Answer» Correct Answer - b | |
| 718. |
For a normal eye, the least distance of distinct vision isA. 0.25 mB. 0.50 mC. 25 mD. Infinite |
| Answer» Correct Answer - a | |
| 719. |
For a normal eye, the least distance of distinct vision is……..and far point is………… .A. 0.25 mB. 0.50 mC. 25 mD. infinite |
|
Answer» Correct Answer - A For normal rye, the least distance of distinct vision is 0.25 m. |
|
| 720. |
What is the least distance of distinct vision for a normal eye ? Is it the same as the distance of near point ? |
| Answer» Correct Answer - `d = 25 cm`. Yes. | |
| 721. |
A prism having an apex angle of `4^@` and refractive index of 1.50 is located in front of a vertical plane mirror as shown in the figure. A horizontal ray of light is incident on the prism. The total angle through which the ray is deviated is: A. `176^(@)`B. `4^(@)`C. `178^(@)`D. `2^(@)` |
|
Answer» Correct Answer - C |
|
| 722. |
Two planoconvex lenses each of the focal length of`10cm`&refractive index`3//2`are placed as shwon .In the space left water`(R.I.=4//3)`is filled.Then whole arrangement is in air.The optical power of the system is(in diopters). A. `6.67`B. `-6.67`C. `33.3`D. `20` |
|
Answer» Correct Answer - A `(1)/(f)=(mu-1)((1)/(R_(1))-(1)/(R_(2)))` `(1)/(10)=(1.5-1)((1)/(oo)-(1)/(-R)) rArr (1)/(10)=(0.5)/(R ) rArr R=5cm` focal length of middle lense `(1)/(f_(2))=(mu-1)((1)/(R_(1))-(1)/(R_(2)))` `(1)/(f_(2))=((4)/(3)-1)((1)/(-5)-(1)/(5))` `(1)/(f_(2))=(1)/(3)xx(-2)/(5)` `(1)/(f_(2))=(-2)/(15)` `(1)/(f_(eq))=(1)/(f_(1))+(1)/(f_(2))+(1)/(f_(3)) rArr (1)/(f_(eq))=(1)/(10)-(2)/(15)+(1)/(10)` `(1)/(f_(eq))=(3-4+3)/(30) rArr (1)/(f_(eq))=(1)/(15)` for combination,`P_(eq)=(100)/(f_(eq))` `P_(eq)=(100)/(15)D rArr P_(eq)=6.67D` |
|
| 723. |
A square wire of side `3.0 cm` is placed `25 cm` away from a concave mirror of focal length `10 cm`. What is the area enclosed by the image of the wire ? The centre of the wire is on the axis of the mirror, with its two sides normal to the axis.A. 4 `cm^(2)`B. 6 `cm^(2)`C. 16 `cm^(2)`D. 36 `cm^(2)` |
|
Answer» Correct Answer - A (a) Linear magnification, `m=I/O=f/(u-f)=10/(25-10)` `m=10/15=2/3` A real magnification=`m^(2)=4/9` Area of image=`4/9xx`area of object =`4/9xx(3)^(2)=4 cm^(2)` |
|
| 724. |
A convex lens has mean focal length of 20 cm. The dispersive power of the material of the lens is 0.02. The longitudinal chromatic aberration for an object at infinity isA. `10^(3)`B. 0.8C. 0.4D. 0.2 |
|
Answer» Correct Answer - C (c ) The separation between the images formed by extreme wavelengths of visible range is called the longitudinal chromatic Is given by, `f_(1)-f_(2)=omegaxxf` Where, `omega` is dispersive power Given, `pmega=0.02,f=20cm` `because f_(1)-f_(2)=0.02xx20=0.40` |
|
| 725. |
A combination of two thin lenses of the same material with focal lengths `f_(1)` and `f_(2)`, arranged on a common axis minimizes chromatic aberration, if the distance between them isA. `((f_(1)+f_(2)))/4`B. `((f_(1)+f_(2)))/2`C. `(f_(1)+f_(2))`D. `2(f_(1)+f_(2))` |
| Answer» Correct Answer - b | |
| 726. |
The dispersive power of the material of lens of focal length `20cm` is `0.8`. The longitudinal chromatic aberration of the lens isA. 0.08 cmB. `0.08//20` cmC. 1.6 cmD. 0.16 cm |
| Answer» Correct Answer - c | |
| 727. |
The proper expsoure time for a photographic print is`20s`at a distance of `0.6m`froma `40`candles power lamb.How long will you expose the same print at a distance of `1.2m`form a `20`candles power lamb? |
|
Answer» In the case of camera,for proper exposure `I_(1)D_(1)^(2)t_(1)=I_(2)D_(2)^(2)t_(2)` As here`D`is constant and `I=(L//r^(2))` `(L_(1))/(r_(2)^(1))xxt_(1)=(L_(2))/(r_(2)^(2))xxt_(2)` `So (40)/(0.6^(2))xx20=(20)/((1.2)^(2))t i.e,t=160sec` |
|
| 728. |
An electric bulb is hanging above the centre of a circular table of radiys 3m at a height of 3m from the its centre. Find the ratio of illuminance at the centre and at a point on the edge of the table. |
|
Answer» Correct Answer - `2sqrt(2):1` |
|
| 729. |
Correct exposure for a photographic print is 10 s at a distance of one metre from a point source of 20 cd. For an equal fogging of the print placed at a distance of 2 m from a 16 cd source, the necessary time for exposure isA. 100 sB. 25 sC. 50 sD. 75 s |
|
Answer» Correct Answer - C (c ) For equal fogging of print, `I_(2)xxt_(2)=I_(1)xxt_(1)` or `L_(2)/r_(2)^(2)xxt_(2)=L_(1)/r_(1)^(2)xxt_(1)` or `16/4xxt_(2)=20/1xx10` `therefore` `t_(2)=50 s` |
|
| 730. |
A bulb of 100 watt is hanging at a height of one meter above the centre of a circular table of diameter 4 m . If the intensity at a point on its rim is `I_(0)` , then the intensity at the centre of the table will beA. `I_(0)`B. `2sqrt(5)I_(0)`C. `2I_(0)`D. `5sqrt(5)I_(0)` |
| Answer» Correct Answer - d | |
| 731. |
Correct exposure for a photographic print is 10 seconds at a distance of one metre from a point source of 20 candela . For an equal fogging of the print placed at a distance of 2 m from a 16 candela source, the necessary time for exposure isA. `100 sec`B. `25 sec`C. `50 sec`D. `75 sec` |
| Answer» Correct Answer - c | |
| 732. |
A point source of 100 candela is held 5 m above a sheet of blotting paper which reflects 75% of light incident upon it. The illuminance of blotting paper isA. 4 photB. 4 luxC. 3 photD. 3 lux |
| Answer» Correct Answer - b | |
| 733. |
1% of light of a source with luminous intensity 50 candela is incident on a circular surface of radius 10 cm . The average illuminance of surface isA. 100 luxB. 200 luxC. 300 luxD. 400 lux |
| Answer» Correct Answer - b | |
| 734. |
Lux is equal toA. `1 "lumen"//m^(2)`B. `1 "lumen"//cm^(2)`C. `1 "candela"//m^(2)`D. `1 "candela"//cm^(2)` |
| Answer» Correct Answer - c | |
| 735. |
An electric lamp is fixed at the ceiling of a circular tunnel as shown is figure. What is the ratio the intensities of light at base A and a point B on the wall A. `1:2`B. `2:sqrt(3)`C. `sqrt(3):1`D. `1:sqrt(2)` |
| Answer» Correct Answer - d | |
| 736. |
If luminous efficiency of a lamp is 2 lumen/watt and its luminous intensity is 42 candela, then power of the lamp isA. `62 W`B. `76 W`C. `138 W`D. `264 W` |
| Answer» Correct Answer - d | |
| 737. |
At what distance form a light source of 64 cd, will the intensity of illumination because 4 flux ? |
|
Answer» Correct Answer - 4m |
|
| 738. |
A small lamp is hung at a height of 8 feet above the centre of a round table of diameter 16 feet . The ratio of intensities of illumination at the centre and at points on the circumference of the table will beA. `1 : 1`B. `2:1`C. `2sqrt(2):1`D. `3:2` |
| Answer» Correct Answer - c | |
| 739. |
An electric bulb illuminates a plane surface. The intensity of illumination on the surface at a point 2 m away from the bulb is `5 xx 10^(-4)` phot `("lumen"//cm^(2))`. The line joining the bulb to the point makes an angle of `60^(@)` with the normal to the surface. The intensity of the bulb in candela isA. `40 sqrt(3)`B. 40C. 20D. `40 xx 10^(-4)` |
| Answer» Correct Answer - b | |
| 740. |
A frosted bulb which may be taken as an isotropic source, gives as illumination of `8lm//m^(2)` at a distance of 5m. Calculate (i) its luminous intensity and (ii) the total luminous flux from the blub. |
|
Answer» Correct Answer - (i) 200 cd (ii) `836 pi lm` |
|
| 741. |
An electric bulb illuminates a plane surface. The intensity of illumination on the surface at a point 2m away from the bulb is `5 xx 10^(-4)` phot. The line joining the bulb to the point makes an angle of `60^(@)` with the normal to the surface. calculate the intensity of the bulb in candela ? (1 phot `= 1m//cm^(2))`. |
|
Answer» Correct Answer - 40 cd |
|
| 742. |
A 60 watt bulb is hung over the center of a table `4 m xx 4 m` at a height of 3 m . The ratio of the intensities of illumination at a point on the centre of the edge and on the corner of the table isA. `(17//13)^(3//2)`B. `2//1`C. `17//13`D. `5//4` |
| Answer» Correct Answer - a | |
| 743. |
(a) Why do spectrum colours recombine on passing through two prisms oriented duly ? (b) What is the essential condition for observing a rainbow ? |
| Answer» The observer must stand with his/her back towards the sun. | |
| 744. |
A candle flame is held `2 metre` above the water level in a tank `4 metre` deep. If `mu` of water is `4//3`, where will image of candle flame be seen ? |
| Answer» The image of candle flame is seen due to reflection of light from water surface in the tank. The image will be at a depth of 2 metre from the surface of water in the tank. | |
| 745. |
An erect image `3 times` the size of the object is obtained with a concave mirror of radius of curvature `36 cm`. What is the position of the object ? |
|
Answer» Here, `m = + 3` (because image is erect) `R = -36 cm, u = ? Let u = -x` As `m = (h_2)/(h_1) = (+ v)/(-u) = 3 :. v = -3 u = 3 x` As `(1)/(u)+(1)/(v)=(1)/(f)=(2)/( R) :. (1)/(-x)+(1)/(3x)=(2)/(-36)` `(-3 + 1)/(3x) = - (1)/(18)` or `3x = 36 :. x = 12 cm` `:. u = -12 cm`. |
|
| 746. |
An object is placed 40 cm from a concave mirror of focal length 20 cm. The image formed isA. Real, inverted and same in sizeB. Real, inverted and smallerC. Virtual, erect and largerD. Virtual, erect and smaller |
| Answer» Correct Answer - a | |
| 747. |
An object 2.5 cm high is placed at a distance of 10 cm from a concave mirror of radius of curvature 30 cm The size of the image isA. 9.2 cmB. 10.5 cmC. 5.6 cmD. 7.5 cm |
| Answer» Correct Answer - d | |
| 748. |
The eye-piece of an astronomical telescope has focal length of 10 cm. The telescope is focused for normal vision of distant objects when the tube length is 1.0 m. Find the focal length of the objective and the magnifying power of the telescope. |
|
Answer» Given, `f_(e)=10 cm, L_(oo)=1.0m=100cm` Since, `L_(oo)=f_(o)+f_(e)` `therefore f_(o)=90.0 cm` Further, magnification, `M_(oo)=(f_(o))/(f_(e))=90.0/10.0=9.0` |
|
| 749. |
Find the size, nature and position of image formed by a concave mirror, when an object of size 1 cm is placed at a distance of 15 cm. Given focal length of mirror is 10 cm. |
|
Answer» Correct Answer - Real, inverted 2 cm high imafe at 30 cm in front of the mirror, `m =- 2` |
|
| 750. |
A lens is placed in the `XYZ`coordinate system such that its optical center is at the original and principal axis is along the `X` axis.The focal length of the lens is`20cm`.A point object has been placed at the point `(-40cm,61cm-1cm)`Which of the following are correct about coordiantes of the image?A. `x=40cm`B. `y=+1cm`C. `z=+1cm`D. `z=-1cm` |
|
Answer» Correct Answer - A,C If object is placed at`-2f`of convex lens so inverted image will be at`2f`so coordiante of image will be `(40cm-1cm,1cm)` |
|