Ray Optics and Optical Instruments Test

Result

Ray Optics and Optical Instruments Test - 1

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Weekly Quiz Competition

Question 1
4 / -1

What can be the largest distance of an image of a real object from a convex mirror of radius of curvature is 20 cm?

A
10 cm

B
20 cm

C
Infinity

D
Zero

Solution

In a convex mirror image is formed only between focus and mirror. So the maximum distance is f i.e, 20/2 = 10cm.
Question 2
4 / -1

A boy of height 1 m stands in front of a convex mirror. His distance from the mirror is equal to its focal length. The height of his image is

A
0.25 m

B
0.33 m

C
0.5 m

D
0.67 m

Solution

Let f be focal length of the convex mirror.
According to new cartesian sign convention
Object distance, u = −f, focal length = +f
Using mirror formula,

The image is formed at a distance f/2 behind the mirror. It is a virtual image.

∴ h₁ = mh₀
Question 3
4 / -1

A concave shaving mirror has a radius of curvature of 35.0 cm. It is positioned so that the (upright) image of a man’s face is 2.50 times the size of the face. How far is the mirror from the face?

A
5.25 cm

B
21.0 cm

C
10.5 cm

D
42 cm

Solution

For spherical mirror, f = R/2
Given, R = 35.0cm or
|f| = 35/2 = 17.5cm

Also, magnification m = −v/u or v = −mu

= −17.5×(0.6)
= −10.5cm
Question 4
4 / -1

A rod of length 10 cm lies along the principal axis of a concave mirror of focal length 10 cm in such way that it end closer to pole is 20 cm away from the mirror. The length of the image is

A
10 cm

B
15 cm

C
2.5 cm

D
5 cm

Solution

Here, f = -10 cm
For end A ,u_A = - 20 cm
Image position v_A of end A is given by

v_A = -20 cm
For end B, u_B = -30 cm
Image position v_B of end B is given by

v_B = −15cm
Length of the image
= |v_A| − |v_B| = 20cm − 15cm = 5cm
Question 5
4 / -1

An object 2 cm high is placed at a distance of 16 cm from a concave mirror, which produces a real image 3 cm high. What is the focal length of the mirror?

A
-9.6 cm

B
-3.6 cm

C
-6.3 cm

D
-8.3 cm

Solution

Here, h₁ = 2 cm, u = -16 cm,
h₂ = -3 cm (Since image is real and inverted.)