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JEE Advanced > Optics

Explore popular questions from Optics for JEE Advanced. This collection covers Optics previous year JEE Advanced questions hand picked by experienced teachers.

Q 1.

Correct4

Incorrect-1

The focal lengths of the objective and the eye piece of a compound microscope are {tex} 2.0 \mathrm { cm } {/tex} and {tex} 3.0 \mathrm { cm } {/tex}, respectively. The distance between the objective and the eye piece is {tex} 15.0 \mathrm { cm } {/tex}. The final image formed by the eye piece is at infinity. The two lenses are thin. The distance in {tex} \mathrm { cm } {/tex} of the object and the image produced by the objective, measured from the objective lens, are respectively

2.4 and 12.0

B

2.4 and 15.0

C

2.0 and 12.0

D

2.0 and 3.0

Explanation



Q 2.

Correct4

Incorrect-1

In a Young's double slit experiment, {tex}12{/tex} fringes are observed to be formed in a certain segment of the screen when light of wavelength {tex} 600 \mathrm { nm } {/tex} is used. If the wavelength of light is changed to {tex} 400 \mathrm { nm } {/tex}, number of fringes observed in the same segment of the screen is given by

A

12

18

C

24

D

30

Explanation

Q 3.

Correct4

Incorrect-1

A given ray of light suffers minimum deviation in an equilateral prism {tex} P {/tex}. Additional prism {tex} Q {/tex} and {tex} R {/tex} of identical shape and of the same material as {tex} P {/tex} are now added as shown in the figure. The ray will now suffer

A

greater deviation

B

no deviation

same deviation as before

D

total internal reflection

Explanation



Q 4.

Correct4

Incorrect-1

An observer can see through a pin-hole the top end of a thin rod of height {tex} \mathrm { h } {/tex}, placed as shown in the figure. The beaker height is {tex} 3 \mathrm { h } {/tex} and its radius {tex} \mathrm { h } {/tex}. When the beaker is filled with a liquid up to a height {tex}2 \mathrm { h } {/tex}, he can see the lower end of the rod. Then the refractive index of the liquid is

A

{tex} \frac { 5 } { 2 } {/tex}

{tex} \sqrt { \frac { 5 } { 2 } } {/tex}

C

{tex} \sqrt { \frac { 3 } { 2 } } {/tex}

D

{tex} \frac { 3 } { 2 } {/tex}

Explanation





Q 5.

Correct4

Incorrect-1

In the ideal double-slit experiment, when a glass-plate (refractive index {tex}1.5 {/tex}) of thickness t is introduced in the path of one of the interfering beams (wave-lenght {tex} \lambda ) , {/tex} the intensity at the position where the central maximum occurred previously remains unchanged. The minimum thickness of the glass-plate is

{tex} 2 \lambda {/tex}

B

{tex} 2 \lambda / 3 {/tex}

C

{tex} \lambda / 3 {/tex}

D

{tex} \lambda {/tex}

Explanation

Q 6.

Correct4

Incorrect-1

In the adjacent diagram, {tex} C P {/tex} represents a wavefront and {tex} A O {/tex} {tex} \& B P , {/tex} the corresponding two rays. Find the condition on {tex} \theta {/tex} for constructive interference at {tex} P {/tex} between the ray {tex} B P {/tex} and reflected ray {tex} O P . {/tex}

A

{tex} \cos \theta = 3 \lambda / 2 d {/tex}

{tex} \cos \theta = \lambda / 4 d {/tex}

C

{tex} \sec \theta - \cos \theta = \lambda / d {/tex}

D

{tex} \sec \theta - \cos \theta = 4 \lambda / d {/tex}

Explanation




Q 7.

Correct4

Incorrect-1

An equilateral prism is placed on a horizontal surface. A ray {tex} P Q {/tex} is incident onto it. For minimum deviation

A

{tex} P Q {/tex} is horizontal

{tex} Q R {/tex} is horizontal

C

{tex} R S {/tex} is horizontal

D

Any one will be horizontal

Explanation

Q 8.

Correct4

Incorrect-1

Focal length of the plano-convex lens is {tex} 15 \mathrm { cm } {/tex}. A small object is placed at {tex} \mathrm { A } {/tex} as shown in the figure. The plane surface is silvered. The image will form at

A

{tex} 60 \mathrm { cm } {/tex} to the left of lens

{tex} 12 \mathrm { cm } {/tex} to the left of lens

C

{tex} 60 \mathrm { cm } {/tex} to the right of lens

D

{tex} 30 \mathrm { cm } {/tex} to the left of lens

Explanation


Q 9.

Correct4

Incorrect-1

Rays of light from Sun falls on a biconvex lens of focal length {tex} f {/tex} and the circular image of Sun of radius {tex} r {/tex} is formed on the focal plane of the lens. Then

A

Area of image is {tex} \pi r ^ { 2 } {/tex} and area is directly proportional of {tex} f {/tex}

Area of image is {tex} \pi r ^ { 2 } {/tex} and area is directly proportional to {tex} f ^ { 2 } {/tex}

C

Intensity of image increases if {tex} { f } {/tex} is increased

D

If lower half of the lens is covered with black paper area will become half

Explanation


Q 10.

Correct4

Incorrect-1

A ray of light traveling in water is incident on its surface open to air. The angle of incidence is {tex} \theta , {/tex} which is less than the critical angle. Then there will be

A

only a reflected ray and no refracted ray

B

only a refracted ray and no reflected ray

a reflected ray and a refracted ray and the angle between them would be less than {tex} 180 ^ { \circ } - 2 \theta {/tex}

D

a reflected ray and a refracted ray and the angle between them would be greater than {tex} 180 ^ { \circ } - 2 \theta {/tex}

Explanation





Q 11.

Correct4

Incorrect-1

A light beam is travelling from Region I to IV (figure). The refractive index in regionals I, II, III and IV are {tex} n _ { 0 } , \frac { n _ { 0 } } { 2 } , \frac { n _ { 0 } } { 6 } {/tex} and {tex} \frac { n _ { 0 } } { 8 } {/tex} respectively. The angle of incidence {tex} \theta {/tex} for which the beam just misses entering region IV is -

A

{tex} \sin ^ { - 1 } ( 3 / 4 ) {/tex}

{tex} \sin ^ { - 1 } ( 1 / 8 ) {/tex}

C

{tex} \sin ^ { - 1 } ( 1 / 4 ) {/tex}

D

{tex} \sin ^ { - 1 } ( 1 / 3 ) {/tex}

Explanation





Q 12.

Correct4

Incorrect-1

A light ray travelling in glass medium is incident on glass- air interface at an angle of incidence {tex} \theta . {/tex} The reflected (R) and transmitted (T) intensities, both as function of {tex} \theta , {/tex} are plotted. The correct sketch is

A

B

D

Explanation

Q 13.

Correct4

Incorrect-1

Young's double slit experiment is carried out by using green, red and blue light, one color at a time. The fringe widths recorded are {tex} b _ { G , } b _ { R } {/tex} and {tex} b _ { B } , {/tex} respectively. Then,

A

{tex} \mathrm { b } _ { G } > \mathrm { b } _ { B } > \mathrm { b } _ { R } {/tex}

B

{tex} \mathrm { b } _ { B } > \mathrm { b } _ { G } > \mathrm { b } _ { R } {/tex}

C

{tex} \mathrm { b } _ { R } > \mathrm { b } _ { B } > \mathrm { b } _ { G } {/tex}

{tex} \mathrm { b } _ { R } > \mathrm { b } _ { G } > \mathrm { b } _ { B } {/tex}

Explanation

Q 14.

Correct4

Incorrect-1

In the Young's double slit experiment using a monochromatic light of wavelength {tex} \lambda , {/tex} the path difference (in terms of an integer {tex} n {/tex} ) corresponding to any point having half the peak intensity is

A

{tex} ( 2 n + 1 ) \frac { \lambda } { 2 } {/tex}

{tex} ( 2 n + 1 ) \frac { \lambda } { 4 } {/tex}

C

{tex} ( 2 n + 1 ) \frac { \lambda } { 8 } {/tex}

D

{tex} ( 2 n + 1 ) \frac { \lambda } { 16 } {/tex}

Explanation

Q 15.

Correct4

Incorrect-1

A point source {tex} S {/tex} is placed at the bottom of a transparent block of height {tex} 10 \mathrm { mm } {/tex} and refractive index {tex} 2.72 . {/tex} It is immersed in a lower refractive index liquid as shown in the figure. It is found that the light emerging from the block to the liquid forms a circular bright spot of diameter {tex} 11.54 \mathrm { mm } {/tex} on the top of the block. The refractive index of the liquid is

A

{tex} 1.21 {/tex}

B

{tex} 1.30 {/tex}

{tex} 1.36 {/tex}

D

{tex} 1.42 {/tex}

Explanation



Q 16.

Correct4

Incorrect-1

A bird is flying up at angle {tex} \sin ^ { - 1 } ( 3 / 5 ) {/tex} with the horizontal. A fish in a pond looks at that bird. When it is vertically above the fish. The angle at which the bird appears to fly (to the fish) is {tex} \left[ n _ { \text {water } } = 4 / 3 \right] {/tex}

A

{tex} \sin ^ { - 1 } ( 3 / 5 ) {/tex}

B

{tex} \sin ^ { - 1 } ( 4 / 5 ) {/tex}

{tex} 45 ^ { \circ } {/tex}

D

{tex} \sin ^ { - 1 } ( 9 / 16 ) {/tex}

Explanation


Q 17.

Correct4

Incorrect-1

A ray of light passes from glass, having a refractive index of {tex} 1.6 , {/tex} to air. The angle of incidence for which the angle of refraction is twice the angle of incidence is

A

{tex} \sin ^ { - 1 } \left( \frac { 4 } { 5 } \right) {/tex}

{tex} \sin ^ { - 1 } \left( \frac { 3 } { 5 } \right) {/tex}

C

{tex} \sin ^ { - 1 } \left( \frac { 5 } { 8 } \right) {/tex}

D

{tex} \sin ^ { - 1 } \left( \frac { 2 } { 5 } \right) {/tex}

Explanation

Q 18.

Correct4

Incorrect-1

Two convex lenses placed in contact form the image of a distant object at {tex} P . {/tex} If the lens {tex} B {/tex} is moved to the right, the image will

A

Move to the left

Move to the right

C

Remain at {tex} P {/tex}

D

Move either to the left or right, depending upon focal lengths of the lenses

Explanation

Q 19.

Correct4

Incorrect-1

A plane glass mirror of thickness {tex} 3 \mathrm { cm } {/tex} of material of {tex} \mu = 3 / 2 {/tex} is silvered on the back surface. When a point object is placed {tex} 9 \mathrm { cm } {/tex} from the front surface of the mirror, then the position of the brightest image from the front surface is

A

{tex} 9 \mathrm { cm } {/tex}

B

{tex} 11 \mathrm { cm } {/tex}

C

{tex} 12 \mathrm { cm } {/tex}

{tex} 13 \mathrm { cm } {/tex}

Explanation


Q 20.

Correct4

Incorrect-1

The graph between object distance {tex}u{/tex} and image distance {tex} v {/tex} for lens is given below. The focal length of the lens is

A

{tex} 5 \pm 0.1 {/tex}

{tex} 5 \pm 0.05 {/tex}

C

{tex} 0.5 \pm 0.1 {/tex}

D

{tex} 0.5 \pm 0.05 {/tex}

Explanation


Q 21.

Correct4

Incorrect-1

A plano-convex lens fits exactly into a plano-concave lens. Their plane surfaces are parallel to each other. If the lenses are made of different material of refractive indices {tex} \mu _ { 1 } {/tex} and {tex} \mu _ { 2 } {/tex} and {tex} R {/tex} is the radius of curvature of the curved surface of the lenses, then focal length of the combination is

{tex} \frac { R } { \mu _ { 1 } - \mu _ { 2 } } {/tex}

B

{tex} \frac { 2 R } { \mu _ { 2 } - \mu _ { 1 } } {/tex}

C

{tex} \frac { R } { 2 \left( \mu _ { 1 } - \mu _ { 2 } \right) } {/tex}

D

{tex} \frac { R } { 2 - \left( \mu _ { 1 } + \mu _ { 2 } \right) } {/tex}

Explanation

Q 22.

Correct4

Incorrect-1

Light from a denser medium 1 passes to a rarer medium 2. When the angle of incidence is {tex} \theta {/tex} the partially reflected and refracted rays are mutually perpendicular. The critical angle will be

A

{tex} \sin ^ { - 1 } ( \cot \theta ) {/tex}

{tex} \sin ^ { - 1 } ( \tan \theta ) {/tex}

C

{tex} \sin ^ { - 1 } ( \cos \theta ) {/tex}

D

{tex} \sin ^ { - 1 } ( \sec \theta ) {/tex}

Explanation


Q 23.

Correct4

Incorrect-1

Refractive index of a prism is {tex} \sqrt { 7 / 3 } {/tex} and the angle of prism is {tex} 60 ^ { \circ } . {/tex} The minimum angle of incidence of a ray that will be transmitted through the prism is

{tex} 30 ^ { \circ } {/tex}

B

{tex} 45 ^ { \circ } {/tex}

C

{tex} 15 ^ { \circ } {/tex}

D

{tex} 50 ^ { \circ } {/tex}

Explanation


Q 24.

Correct4

Incorrect-1

A convex lens of power {tex} + 6 {/tex} dioptre is placed in contact with a concave lens of power {tex} - 4 {/tex} dioptre. What will be the nature and focal length of this combination?

A

Concave, {tex} 25 \mathrm { cm } {/tex}

Convex, {tex} 50 \mathrm { cm } {/tex}

C

Concave, {tex} 20 \mathrm { cm } {/tex}

D

Convex, {tex} 100 \mathrm { cm } {/tex}

Explanation

Q 25.

Correct4

Incorrect-1

Figure (a) shows two plane-convex lenses in contact as shown. The combination has focal length {tex} 24 \mathrm { cm } . {/tex} Figure (b) shows the same with a liquid introduced between them. If refractive index of glass of the lenses is {tex}1.50{/tex} and that of the liquid is {tex} 1.60 , {/tex} the focal length of system in figure(b) will be

{tex} - 120 \mathrm { cm } {/tex}

B

{tex} 120 \mathrm { cm } {/tex}

C

{tex} - 24 \mathrm { cm } {/tex}

D

{tex} 24 \mathrm { cm } {/tex}

Explanation