NEET Ray Optics — Set 9

Question 1

A simple microscope with a focal length of $ 8 \, \text{cm} $ forms an image at infinity. What is the magnification?

Accepted Answer

Magnification at infinity: $ m = \frac{D}{f} $. $ D = 25 \, \text{cm} $, $ f = 8 \, \text{cm} $. $ m = \frac{25}{8} = 3.125 $.

Question 2

A telescope has an objective of focal length $ 140 \, \text{cm} $ and an eyepiece of focal length $ 7 \, \text{cm} $. What is its magnifying power?

Accepted Answer

Magnifying power: $ m = \frac{f_o}{f_e} $. $ f_o = 140 \, \text{cm} $, $ f_e = 7 \, \text{cm} $. $ m = \frac{140}{7} = 20 $.

Question 3

What is the primary optical phenomenon responsible for the mirage effect observed on hot roads?

Accepted Answer

The mirage effect on hot roads results from total internal reflection. Hot air near the ground has a lower refractive index than cooler air above, causing light from the sky to bend upward when the angle of incidence exceeds the critical angle, creating an illusion of water.

NEET Physics: Ray Optics — Practice Set 9

Q1. A simple microscope with a focal length of \( 8 \, \text{cm} \) forms an image at infinity. What is the magnification?

Q2. A telescope has an objective of focal length \( 140 \, \text{cm} \) and an eyepiece of focal length \( 7 \, \text{cm} \). What is its magnifying power?

Q3. What is the primary optical phenomenon responsible for the mirage effect observed on hot roads?

Q4. A lens has a power of \( +4 \, \text{D} \). What is its focal length in centimeters?

Q5. A converging beam meets a concave lens (\( f = 20 \, \text{cm} \)) \( 8 \, \text{cm} \) before the convergence point. What is the new image distance?

Q6. What is the critical angle for a diamond (\( n = 2.42 \)) to glass (\( n = 1.5 \)) interface?

Q7. A converging beam of light meets a concave lens of focal length \( 25 \, \text{cm} \) at \( 10 \, \text{cm} \) before the convergence point. What is the new convergence distance from the lens?

Q8. A compound microscope has an objective of focal length \( 1 \, \text{cm} \) and eyepiece of focal length \( 5 \, \text{cm} \) with a tube length of \( 15 \, \text{cm} \). What is the magnification at infinity?

Q9. A concave mirror of focal length \( 6 \, \text{cm} \) has an object placed \( 12 \, \text{cm} \) from it. What is the image distance?

Q10. A concave lens of focal length \( 15 \, \text{cm} \) has an object placed \( 30 \, \text{cm} \) from it. What is the image distance?

Q11. A prism of angle \( 60^\circ \) and refractive index \( 1.5 \) produces a minimum deviation of \( 30^\circ \). What is the angle of incidence?

Q12. A ray of light passes from air (\( n = 1 \)) to glass (\( n = 1.5 \)) at an angle of incidence of \( 40^\circ \). What is the angle of refraction?

Q13. A convex lens (\( f = 30 \, \text{cm} \)) and a concave lens (\( f = 60 \, \text{cm} \)) are in contact. What is the effective focal length?

Q14. What is the significance of the critical angle in the context of total internal reflection?

Q15. What is the critical angle for a glass (\( n = 1.5 \)) to water (\( n = 1.33 \)) interface?