NEET Ray Optics — Set 19

Question 1

A simple microscope with a lens of focal length $ 10 \, \text{cm} $ forms an image at the least distance of distinct vision ($ 25 \, \text{cm} $). What is the magnification?

Accepted Answer

Magnification: $ m = 1 + \frac{D}{f} $. $ D = 25 \, \text{cm} $, $ f = 10 \, \text{cm} $. $ m = 1 + \frac{25}{10} = 1 + 2.5 = 3.5 $.

Question 2

A prism of angle $ 30^\circ $ and refractive index $ 1.6 $ produces what minimum deviation?

Accepted Answer

For a thin prism: $ D_m = (n - 1) A $. $ n = 1.6 $, $ A = 30^\circ $. $ D_m = (1.6 - 1) \times 30 = 0.6 \times 30 = 18^\circ $.

Question 3

A convex lens of focal length $ 20 \, \text{cm} $ forms an image at $ 40 \, \text{cm} $ from the lens. What is the object distance?

Accepted Answer

Focal length: $ f = 20 \, \text{cm} $. Image distance: $ v = 40 \, \text{cm} $ (real image). Lens formula: $ \frac{1}{v} - \frac{1}{u} = \frac{1}{f} $. $ \frac{1}{40} - \frac{1}{u} = \frac{1}{20} \Rightarrow \frac{1}{u} = \frac{1}{40} - \frac{1}{20} = \frac{1 - 2}{40} = \frac{-1}{40} $. $ u = -40 \, \text{cm} $.

NEET Physics: Ray Optics — Practice Set 19

Q1. A simple microscope with a lens of focal length \( 10 \, \text{cm} \) forms an image at the least distance of distinct vision (\( 25 \, \text{cm} \)). What is the magnification?

Q2. A prism of angle \( 30^\circ \) and refractive index \( 1.6 \) produces what minimum deviation?

Q3. A convex lens of focal length \( 20 \, \text{cm} \) forms an image at \( 40 \, \text{cm} \) from the lens. What is the object distance?

Q4. What ensures that a convex mirror produces an image smaller than the object at all positions?

Q5. A prism of angle \( 40^\circ \) and refractive index \( 1.5 \) produces what minimum deviation?

Q6. A concave mirror of radius of curvature \( 30 \, \text{cm} \) has an object placed \( 45 \, \text{cm} \) from it. What is the image distance?

Q7. A lens has a power of \( +3 \, \text{D} \). What is its focal length in centimeters?

Q8. A converging beam meets a convex lens (\( f = 15 \, \text{cm} \)) \( 10 \, \text{cm} \) before the convergence point. What is the new image distance?

Q9. A compound microscope has an objective of focal length \( 1.25 \, \text{cm} \) and eyepiece of focal length \( 5 \, \text{cm} \) with a tube length of \( 15 \, \text{cm} \). What is the magnification at infinity?

Q10. A compound microscope has an objective of focal length \( 2 \, \text{cm} \) and tube length \( 20 \, \text{cm} \). If the eyepiece magnification is \( 5 \), what is the total magnification?