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

## Chemistry

Optics

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Q 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

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Q 2. 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

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Q 3. 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

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Q 4. 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

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Q 5. 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

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Q 6. 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

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Q 7. The apparent thickness of a thick plano-convex lens is measured once with the plane face upward and then with the convex face upward. The value will be

A

More in the first case

B

Same in the two cases

More in the second case

D

Any of the above depending on the value of its actual thickness

##### Explanation

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Q 8. Two thin lenses are placed {tex} 5 \mathrm { cm } {/tex} apart along the same axis and illuminated with a beam of light parallel to that axis. The first lens in the path of the beam is a converging lens of focal length {tex} 10 \mathrm { cm } {/tex} whereas the second is a diverging lens of focal length {tex} 5 \mathrm { cm } . {/tex} If the second lens is now moved toward the first, the emergent light

A

Remains parallel

B

Remains convergent

C

Remains divergent

Changes from parallel to divergent

##### Explanation

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Q 9. A point object {tex} ^ { \prime } O ^ { \prime } {/tex} is at the centre of curvature of a concave mirror. The mirror starts to move at a speed {tex} u {/tex}, in a direction perpendicular to the principal axis. Then, the initial velocity of the image is

A

{tex} 2 u , {/tex} in the direction opposite to that of mirror's velocity

{tex} 2 u , {/tex} in the direction same as that of mirror's velocity

C

Zero

D

{tex} u , {/tex} in the direction same as that of mirror's velocity

##### Explanation

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Q 10. An object is approaching a fixed plane mirror with velocity {tex} 5 \mathrm { ms } ^ { - 1 } {/tex} making an angle of {tex} 45 ^ { \circ } {/tex} with the normal. The speed of image w.r.t the mirror is

{tex} 5 \mathrm { ms } ^ { - 1 } {/tex}

B

{tex} 5 / \sqrt { 2 } \mathrm { ms } ^ { - 1 } {/tex}

C

{tex} 5 \sqrt { 2 } \mathrm { ms } ^ { - 1 } {/tex}

D

{tex} 10 \mathrm { ms } ^ { - 1 } {/tex}

##### Explanation

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Q 11. Two wavelengths of light {tex} \lambda _ { 1 } {/tex} and {tex} \lambda _ { 2 } {/tex} are sent through a Young's double-slit apparatus simultaneously. If the third-order bright fringe coincides with the fourth-order bright fringe, then

{tex} \frac { \lambda _ { 1 } } { \lambda _ { 2 } } = \frac { 4 } { 3 } {/tex}

B

{tex} \frac { \lambda _ { 1 } } { \lambda _ { 2 } } = \frac { 3 } { 4 } {/tex}

C

{tex} \frac { \lambda _ { 1 } } { \lambda _ { 2 } } = \frac { 5 } { 4 } {/tex}

D

{tex} \frac { \lambda _ { 1 } } { \lambda _ { 2 } } = \frac { 4 } { 5 } {/tex}

##### Explanation

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Q 12. In Young's double-slit experiment, how many maximas can be obtained on a screen (including the central maximum) on both sides of the central fringe {tex} ( \lambda = 2000 \mathrm { Å} ) ? {/tex}

A

12

7

C

18

D

4

##### Explanation

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Q 13. A beam of electron is used in an YDSE experiment. The slit width is {tex} d {/tex}. When the velocity of electron is increased, then

A

No interference is observed

B

Fringe width increases

Fringe width decreases

D

Fringe width remains same

##### Explanation

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Q 14. A ray of light of intensity {tex} I {/tex} is incident on a parallel glass-slab at a point {tex} A {/tex} as shown in fig. It undergoes partial reflection and refraction. At each reflection {tex} 25 \% {/tex} of incident energy is reflected. The rays {tex} A B {/tex} and{tex} A ^ { \prime } B ^ { \prime } {/tex} undergo interference. The ratio {tex} I _ { \max } / I _ { \min } {/tex} is

A

4:1

B

8:1

C

7:1

49:1

##### Explanation

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Q 15. If the distance between the first maxima and fifth minima of a double-slit pattern is {tex} 7 \mathrm { mm } {/tex} and the slits are separated by {tex} 0.15 \mathrm { mm } {/tex} with the screen {tex} 50 \mathrm { cm } {/tex} from the slits, then wavelength of the light used is

{tex} 600 \mathrm { nm } {/tex}

B

{tex} 525 \mathrm { nm } {/tex}

C

{tex} 467 \mathrm { nm } {/tex}

D

{tex} 420 \mathrm { nm } {/tex}