NEET Ray Optics — Set 1

Question 1

What is the primary condition under which a convex lens forms a virtual and magnified image?

Accepted Answer

For a convex lens, a virtual and magnified image is formed when the object is placed between the focal point (F) and the optical center (O). In this position, the rays diverge after refraction, and their backward extensions converge on the same side as the object, producing a virtual, erect, and magnified image.

Question 2

An object is placed $ 25 \, \text{cm} $ from a concave mirror of radius of curvature $ 40 \, \text{cm} $. What is the image distance?

Accepted Answer

Focal length: $ f = \frac{R}{2} = \frac{-40}{2} = -20 \, \text{cm} $. Object distance: $ u = -25 \, \text{cm} $. Mirror equation: $ \frac{1}{v} + \frac{1}{-25} = \frac{1}{-20} \Rightarrow \frac{1}{v} = \frac{1}{-20} + \frac{1}{25} = \frac{-5 + 4}{100} = \frac{-1}{100} $. $ v = -100 \, \text{cm} $.

Question 3

What is the critical angle for a glass ($ n = 1.52 $) to air interface?

Accepted Answer

Critical angle: $ \sin i_c = \frac{n_2}{n_1} $. Glass ($ n_1 = 1.52 $), air (\コンパクト n_2 = 1 \)). $ \sin i_c = \frac{1}{1.52} \approx 0.658 $. $ i_c = \sin^{-1}(0.658) \approx 41.1^\circ $.

NEET Physics: Ray Optics — Practice Set 1

Q1. What is the primary condition under which a convex lens forms a virtual and magnified image?

Q2. An object is placed \( 25 \, \text{cm} \) from a concave mirror of radius of curvature \( 40 \, \text{cm} \). What is the image distance?

Q3. What is the critical angle for a glass (\( n = 1.52 \)) to air interface?

Q4. A double convex lens of refractive index \( 1.5 \) has radii of curvature \( 12 \, \text{cm} \) and \( -12 \, \text{cm} \). What is its focal length?

Q5. A concave mirror of focal length \( 15 \, \text{cm} \) forms an image at \( 30 \, \text{cm} \) from the mirror. What is the object distance?

Q6. A prism of angle \( 60^\circ \) and refractive index \( 1.5 \) is placed in water (\( n = 1.33 \)). What is the new minimum deviation?

Q7. In a concave mirror, when an object is placed beyond the center of curvature, what is the nature of the image formed?

Q8. Why does a convex lens form a real image only when the object is outside the focal point?

Q9. A convex lens has a power of \( +5 \, \text{D} \). What is its focal length in centimeters?

Q10. What is the critical angle for a water-air interface (\( n_{\text{water}} = 1.33 \))?

Q11. A convex lens of focal length \( 15 \, \text{cm} \) has an object placed \( 30 \, \text{cm} \) from it. What is the magnification?

Q12. Why does the image formed by a convex lens become real and inverted when the object is moved beyond the focal point?

Q13. A convex mirror of radius of curvature \( 40 \, \text{cm} \) forms an image \( 10 \, \text{cm} \) behind the mirror. What is the object distance?

Q14. A convex lens of focal length \( 25 \, \text{cm} \) forms an image at \( 50 \, \text{cm} \) from the lens. What is the object distance?

Q15. A prism of angle \( 60^\circ \) and refractive index \( 1.45 \) produces what minimum deviation?