Geometrical Optics | Physics JEE previous year questions with Solutions

Q 11 :

The light rays from an object have been reflected towards an observer from a standard flat mirror, the image observed by the observer are

A. Real
B. Erect
C. Smaller in size than object
D. Laterally inverted

Choose the most appropriate answer from the options given below: [2023]

B and C only
A, C and D only
B and D only
A and D only

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(3)

Plane mirror forms erect, same sized, laterally inverted and virtual image of real object.

Q 12 :

Two objects A and B are placed at 15 cm and 25 cm from the pole in front of a concave mirror having radius of curvature 40 cm. The distance between images formed by the mirror is: [2023]

40 cm
60 cm
160 cm
100 cm

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(3)

$by mirror formula \frac{1}{v} + \frac{1}{u} = \frac{1}{f}$

$\frac{1}{v_{1}} + \frac{1}{- 15} = \frac{1}{- 20}$

$\frac{1}{v_{1}} = - \frac{1}{20} + \frac{1}{15} = \frac{- 3 + 4}{60} \Rightarrow v_{1} = 60 cm$

$\frac{1}{v_{2}} + \frac{1}{- 25} = \frac{1}{- 20}$

$\frac{1}{v_{2}} = \frac{- 1}{20} + \frac{1}{25} = \frac{- 5 + 4}{100} = \frac{- 1}{100}$

$\Rightarrow v_{2} = - 100 cm$

$d = 60 + 100 = 160 cm$

Q 13 :

An object is placed at a distance of 12 cm in front of a plane mirror. The virtual and erect image is formed by the mirror. Now the mirror is moved by 4 cm towards the stationary object. The distance by which the position of image would be shifted, will be: [2023]

4 cm towards mirror
8 cm towards mirror
8 cm away from mirror
2 cm towards mirror

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(2)

$∴$ Shifting of image will be 8 cm towards mirror.

Q 14 :

When one light ray is reflected from a plane mirror with 30° angle of reflection, the angle of deviation of the ray after reflection is [2023]

140°
120°
110°
130°

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(2)

Q 15 :

In an experiment for estimating the value of focal length of a converging mirror, the image of an object placed at 40 cm from the pole of the mirror is formed at a distance 120 cm from the pole of the mirror. These distances are measured with a modified scale in which there are 20 small divisions in 1 cm. The value of error in measurement of focal length of the mirror is 1/K cm. The value of K is _____. [2023]

0%

(32)

$\frac{1}{v} + \frac{1}{u} = \frac{1}{f}$

$\frac{- 1}{120} - \frac{1}{40} = \frac{1}{f}, f = - 30 cm$

$Now, \frac{- 1}{v^{2}} d v - \frac{1}{u^{2}} d u = - \frac{1}{f^{2}} d f$

$Also d v = d u = \frac{1}{20} cm$

$∴$ $\frac{\frac{1}{20}}{{(120)}^{2}} + \frac{\frac{1}{20}}{{(40)}^{2}} = \frac{d f}{{(30)}^{2}}$

$On solving d f = \frac{1}{32} cm \Rightarrow k = 32$

Q 16 :

A thin cylindrical rod of length 10 cm is placed horizontally on the principal axis of a concave mirror of focal length 20 cm. The rod is placed in a such a way that the midpoint of the rod is at 40 cm from the pole of the mirror. The length of the image formed by the mirror will be $\frac{x}{3} m$ . The value of $x$ is _______. [2023]

0%

(32)

$U_{A} = - 45 cm, f = - 20 cm$

$V_{A} = \frac{- 45 \times (- 20)}{- 45 - (- 20)} = \frac{- 900}{25} = - 36 cm$

$And U_{B} = - 35 cm$

$∴$ $V_{B} = \frac{- 35 \times (- 20)}{- 35 - (- 20)} = \frac{700}{- 15} = - \frac{140}{3} cm$

$∴$ $V_{A} - V_{B} = length of image$

$= (- 36 + \frac{140}{3}) cm = \frac{- 108 + 140}{3} cm = \frac{32}{3} cm$

$∴$ $x = 32$

Q 17 :

Two vertical parallel mirrors A and B are separated by 10 cm. A point object O is placed at a distance of 2 cm from mirror A. The distance of the second nearest image behind mirror A from the mirror A is ________ cm. [2023]

0%

(18)

The desired image is 18 cm from A.

Q 18 :

As shown in the figure, a plane mirror is fixed at a height of 50 cm from the bottom of a tank containing water $(μ = \frac{4}{3})$ . The height of water in the tank is 8 cm. A small bulb is placed at the bottom of the water tank. The distance of image of the bulb formed by mirror from the bottom of the tank is _________ cm. [2023]

0%

(98)

$Apparent depth of O = \frac{d}{μ} = 6$

$Distance between O and I_{2} = 48 + 50 = 98 cm$

Q 19 :

Distance between an object and three times magnified real image is 40 cm. The focal length of the mirror used is ______ cm. [2026]

− 20
− 15/2
− 10
− 15

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(4)

Topic Question Set