# NEET

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

## Biology

Optics

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Q 1. A double convex lens is made of glass which has its refractive index 1.45 for violet rays and 1.50 for red rays. If the focal length for violet ray is 20cm the focal length for red ray will be

A

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

18{tex} \mathrm { cm } {/tex}

C

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

D

22{tex} \mathrm { cm } {/tex}

##### Explanation

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Q 2. If the refractive index of the material of a prism is {tex} \cot \frac { \mathrm { A } } { 2 } {/tex} and the angle of prism is {tex} \mathrm { A } {/tex} , then angle of minimum deviation is

{tex} \pi - 2 A {/tex}

B

{tex} \pi - A {/tex}

C

{tex} \frac { \pi } { 2 } - 2 { A } {/tex}

D

{tex} \frac { \pi } { 2 } - A {/tex}

##### Explanation

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Q 3. If two {tex} + 5 {/tex} diopter lenses are mounted at some distance apart, the equivalent power will always be negative if the distance is

greater than 40{tex} \mathrm { cm } {/tex}

B

equal to 40{tex} \mathrm { cm } {/tex}

C

equal to 10{tex} \mathrm { cm } {/tex}

D

less than 10{tex} \mathrm { cm } {/tex}

##### Explanation

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Q 4. Refraction of light from air to glass and from air to water are shown in figure (i) and figure (ii) below. The value of the angle {tex} \theta {/tex} in the case of refraction as shown in figure (iii) will be

A

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

{tex} 35 ^ { \circ } {/tex}

C

{tex} 60 ^ { \circ } {/tex}

D

{tex} 41 ^ { \circ } {/tex}

##### Explanation

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Q 5. A fish looking up through the water sees the outside world contained in a circular horizon. If the refractive index of water is {tex} \frac { 4 } { 3 } {/tex} and the fish is 12{tex} \mathrm { cm } {/tex} below the surface, the radius of this circle in {tex} \mathrm { cm } {/tex} is

A

{tex} 36\sqrt { 5 } {/tex}

B

{tex} 4\sqrt { 5 } {/tex}

C

{tex} 36\sqrt { 7 } {/tex}

{tex} 36/ \sqrt { 7 } {/tex}

##### Explanation

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Q 6. If {tex} f _ { V } {/tex} and {tex} f _ { R } {/tex} are the focal lengths of a convex lens for violet and red light respectively and {tex} F _ { V } {/tex} and {tex} F _ { R } {/tex} are the focal lengths of concave lens for violet and red light respectively, then we have

{tex} f _ { V } < f _ { R } {/tex} and {tex} F _ { V } > F _ { R } {/tex}

B

{tex} f _ { V } < f _ { R } {/tex} and {tex} F _ { V } < F _ { R } {/tex}

C

{tex} f _ { V } > f _ { R } {/tex} and {tex} F _ { V } > F _ { R } {/tex}

D

{tex} f _ { V } > f _ { R } {/tex} and {tex} F _ { V } < F _ { R } {/tex}

##### Explanation

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Q 7. Spherical aberration in a lens:

A

is minimum when most of the deviation is at first surface

B

is minimum when most of the deviation is at the second surface

is minimum when the total deviation is equally distributed over the two surfaces

D

does not depend on the above considerations

##### Explanation

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Q 8. A telescope consists of two thin lenses of focal lengths, 0.3 {tex} \mathrm { m } {/tex} and 3{tex} \mathrm { cm } {/tex} respectively. It is focused on moon which subtends an angle of {tex} 0.5 ^ { \circ } {/tex} at the objective. Then the angle subtended at the eye by the final image will be

{tex} 5 ^ { \circ } {/tex}

B

{tex} 0.25 ^ { \circ } {/tex}

C

{tex} 0.5 ^ { \circ } {/tex}

D

{tex} 0.35 ^ { \circ } {/tex}

##### Explanation

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Q 9. The layered lens as shown is made of two types of transparent materials-one indicated by horizontal lines and the other by vertical lines. The number of images formed of an object will be

A

1

2

C

3

D

6

##### Explanation

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Q 10. A man's near point is 0.5{tex} \mathrm { m } {/tex} and far point is 3{tex} \mathrm { m } . {/tex} Power of spectacle lenses required for (i) reading purposes, (ii) seeing distant objects, respectively, are

A

{tex} - 2 \mathrm D{/tex} and {tex}+3 \mathrm D {/tex}

B

{tex} + 2 \mathrm { D } {/tex} and {tex} - 3 \mathrm { D } {/tex}

{tex} + 2 \mathrm { D } {/tex} and {tex} - 0.33 \mathrm { D } {/tex}

D

{tex} - 2 \mathrm { D } {/tex} and {tex} + 0.33 \mathrm { D } {/tex}

##### Explanation

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Q 11. A ray of light falls on a transparent glass slab of refractive index {tex} 1.62 . {/tex} If the reflected ray and the refracted ray are mutually perpendicular, the angle of incidence is

{tex} \tan ^ { - 1 } ( 1.62 ) {/tex}

B

{tex} \tan ^ { - 1 } \left( \frac { 1 } { 1.62 } \right) {/tex}

C

{tex} \tan ^ { - 1 } ( 1.33 ) {/tex}

D

{tex} \tan ^ { - 1 } \left( \frac { 1 } { 1.33 } \right) {/tex}

##### Explanation

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Q 12. A telescope has an objective of focal length {tex} 100\mathrm { cm } {/tex} and an eyepiece of focal length {tex} 5 \mathrm { cm } . {/tex} What is the magnifying power of the telescope when the final image is formed at the least distance of distinct vision?

A

20

24

C

28

D

32

##### Explanation

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Q 13. Which light rays undergoes two internal reflection inside a raindrop, which of the rainbow is formed?

A

Primary rainbow

Secondary rainbow

C

Both (a) and (b)

D

Can't say

##### Explanation

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Q 14. When a plane mirror is placed horizontally on a level ground at a distance of {tex}60 \mathrm { m } {/tex} from the foot of a tower, the top of the tower and its image in the mirror subtend an angle of {tex} 90 ^ { \circ } {/tex} at the eye. The height of the tower will be

A

30{tex} \mathrm { m } {/tex}

60{tex} \mathrm { m } {/tex}

C

90{tex} \mathrm { m } {/tex}

D

120{tex} \mathrm { m } {/tex}

##### Explanation

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Q 15. A parallel beam of light is incident on the surface of a transparent hemisphere of radius {tex} R {/tex} and refractive index {tex}2.0{/tex} as shown in figure. The position of the image formed by refraction at the first surface is:

A

{tex} R / 2 {/tex}

B

{tex} R {/tex}

{tex}2 R {/tex}

D

{tex}3 R {/tex}

##### Explanation

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Q 16. For a prism kept in air it is found that for an angle of incidence {tex} 60 ^ { \circ } , {/tex} the angle of Prism {tex} \mathrm { A } {/tex} , angle of deviation {tex} \delta {/tex} and angle of emergence '{tex} e{/tex}' become equal. Then the refractive index of the prism is

1.73

B

1.15

C

15

D

1.33

##### Explanation

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Q 17. A person can see clearly only upto a distance of {tex} 30 \mathrm { cm } . {/tex} He wants to read a book placed at a distance of {tex} 50\mathrm { cm } {/tex} from his eyes. What is the power of the lens of his spectacles?

A

{tex} - 1.0 \mathrm D {/tex}

{tex} - 1.33 \mathrm { D } {/tex}

C

{tex} - 1.67\mathrm D {/tex}

D

{tex} - 2.0 \mathrm { D } {/tex}

##### Explanation

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Q 18. A vessel of depth x is half filled with oil of refractive index {tex}\mu_{1}{/tex} and the other half is filled with water of refractive index {tex}\mu_{2}{/tex}.The apparent depth of the vessel when viewed from above is

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

B

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

C

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

D

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

##### Explanation

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Q 19. The following figure shows refraction of light at the interface of three media. Correct order of optical density (d) of the media is

A

{tex} d _ { 1 } > d _ { 2 } > d _ { 3 } {/tex}

B

{tex} d _ { 2 } > d _ { 1 } > d _ { 3 } {/tex}

C

{tex} d _ { 3 } > d _ { 3 } > d _ { 2 } {/tex}

{tex} d _ { 2 } > d _ { 3 } > d _ { 1 } {/tex}

##### Explanation

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Q 20. The refractive index of a glass is {tex}1.520{/tex} for red light and {tex}1.525{/tex} for blue light. Let {tex} D _ { 1 } {/tex} and {tex} D _ { 2 } {/tex} be angles of minimum deviation for red and blue light respectively in a prism of this glass. Then,

{tex} D _ { 1 } < D _ { 2 } {/tex}

B

{tex} D _ { 1 } = D _ { 2 } {/tex}

C

{tex} D _ { 1 } {/tex} can be less than or greater than {tex} D _ { 2 } {/tex} depending upon the angle of prism

D

{tex} D _ { 1 } > D _ { 2 } {/tex}

##### Explanation

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Q 21. Which of the following is not due to total internal reflection?

A

Working of optical fibre

Difference between apparent and real depth of pond

C

Mirage on hot summer days

D

Brilliance of diamond

##### Explanation

Apparent depth of the pond appears to be less than the real depth only because of refraction of light, but not because of total internal reflection. On the other hand, brilliance of diamond, formation of mirage on hot summer days and working of optical fiber are based on total internal reflection.

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Q 22. A body is located on a wall. Its image of equal size is to be obtained on a parallel wall with the help of a convex lens. The lens is placed at a distance 'd' ahead of second wall, then the required focal length will be

A

only {tex} \frac { d } { 4 } {/tex}

only {tex} \frac { d } { 2 } {/tex}

C

more than {tex} \frac { d } { 4 } {/tex} but less than {tex} \frac { d } { 2 } {/tex}

D

less than {tex} \frac { d } { 4 } {/tex}

##### Explanation

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Q 23. 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 be to make the

image less bright.

B

lower half of the image disappear.

C

upper half of the image disappear.

D

image blurred.

##### Explanation

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Q 24. Light propagates with speed of {tex} 2.2 \times 10 ^ { 8 } \mathrm { m } / \mathrm { s } {/tex} and {tex} 2.4 \times 10 ^ { 8 } \mathrm { m } / \mathrm { s } {/tex} in the media {tex} \mathrm { P } {/tex} and {tex} \mathrm { Q } {/tex} respectively. The critical angle of incidence for light undergoing reflection from {tex} \mathrm { P } {/tex} and {tex} \mathrm { Q } {/tex} is

A

{tex} \sin ^ { - 1 } \left( \frac { 1 } { 11 } \right) {/tex}

{tex} \sin ^ { - 1 } \left( \frac { 11 } { 12 } \right) {/tex}

C

{tex} \sin ^ { - 1 } \left( \frac { 5 } { 12 } \right) {/tex}

D

{tex} \sin ^ { - 1 } \left( \frac { 5 } { 11 } \right) {/tex}

##### Explanation

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Q 25. In young's double-slit experiment, the intensity of light at a point on the screen where the path difference is {tex} \lambda {/tex} is {tex}I{/tex}, {tex} \lambda {/tex} being the wavelength of light used. The intensity at a point where the path difference is {tex} \frac { \lambda } { 4 } {/tex} will be

A

{tex} \frac { I } { 4 } {/tex}

{tex} \frac { I } { 2 } {/tex}

C

{tex}I{/tex}

D

zero