NEET Ray Optics — Set 2

Question 1

Why does a plane mirror not produce magnification greater than unity?

Accepted Answer

A plane mirror reflects light such that the image distance equals the object distance, and the image is formed by direct reflection without convergence or divergence. This results in an image of the same size as the object, with a magnification of 1, as there’s no mechanism to alter the apparent size.

Question 2

A telescope has an objective of focal length $ 160 \, \text{cm} $ and an eyepiece of focal length $ 8 \, \text{cm} $. What is its magnifying power?

Accepted Answer

Magnifying power: $ m = \frac{f_o}{f_e} $. $ f_o = 160 \, \text{cm} $, $ f_e = 8 \, \text{cm} $. $ m = \frac{160}{8} = 20 $.

Question 3

An object is placed $ 14 \, \text{cm} $ from a convex mirror of focal length $ 28 \, \text{cm} $. What is the magnification?

Accepted Answer

Focal length: $ f = 28 \, \text{cm} $, $ u = -14 \, \text{cm} $. Mirror equation: $ \frac{1}{v} + \frac{1}{-14} = \frac{1}{28} \Rightarrow \frac{1}{v} = \frac{1}{28} + \frac{1}{14} = \frac{1 + 2}{28} = \frac{3}{28} $. $ v = \frac{28}{3} \approx 9.33 \, \text{cm} $. Magnification: $ m = -\frac{v}{u} = -\frac{9.33}{-14} \approx 0.666 $.

NEET Physics: Ray Optics — Practice Set 2

Q1. Why does a plane mirror not produce magnification greater than unity?

Q2. A telescope has an objective of focal length \( 160 \, \text{cm} \) and an eyepiece of focal length \( 8 \, \text{cm} \). What is its magnifying power?

Q3. An object is placed \( 14 \, \text{cm} \) from a convex mirror of focal length \( 28 \, \text{cm} \). What is the magnification?

Q4. An object is at a depth of \( 15 \, \text{cm} \) in water (\( n = 1.5 \)). What is the apparent depth?

Q5. An object is placed \( 20 \, \text{cm} \) from a concave mirror of focal length \( 8 \, \text{cm} \). What is the image distance?

Q6. A simple microscope with a focal length of \( 4 \, \text{cm} \) forms an image at \( 25 \, \text{cm} \). What is the magnification?

Q7. A prism of refracting angle \( 30^\circ \) and refractive index \( 1.6 \) produces what minimum deviation?

Q8. A ray of light passes from water (\( n = 1.33 \)) to air at an angle of incidence of \( 49^\circ \). What happens?

Q9. A glass slab (\( n = 1.5 \)) of thickness \( 6 \, \text{cm} \) is placed over a point. What is the apparent shift?

Q10. A simple microscope with a focal length of \( 6 \, \text{cm} \) forms an image at infinity. What is the magnification?

Q11. A prism of angle \( 45^\circ \) has a refractive index of \( 1.5 \). What is the angle of minimum deviation?

Q12. A compound microscope has an objective of focal length \( 2.5 \, \text{cm} \) and eyepiece of focal length \( 5 \, \text{cm} \) with a tube length of \( 20 \, \text{cm} \). What is the magnification at infinity?

Q13. A prism of angle \( 45^\circ \) has a refractive index of \( 1.6 \). What is the angle of minimum deviation?

Q14. Why can’t a concave mirror form an image at infinity when the object is placed at any finite distance?

Q15. A convex mirror of focal length \( 12 \, \text{cm} \) forms an image \( 6 \, \text{cm} \) behind the mirror. What is the object distance?