NEET Ray Optics — Set 17

Question 1

An object is at a depth of $ 19.95 \, \text{cm} $ in a medium with refractive index $ 1.5 $. What is the apparent depth?

Accepted Answer

Apparent depth = $ \frac{\text{real depth}}{n} $. Real depth = $ 19.95 \, \text{cm} $, $ n = 1.5 $. Apparent depth = $ \frac{19.95}{1.5} = 13.3 \, \text{cm} $.

Question 2

Why does a concave mirror form a real image when the object is placed beyond the focal point?

Accepted Answer

When the object is beyond the focal point of a concave mirror, the reflected rays converge to a point on the same side as the object. This convergence of actual rays results in a real image that can be projected onto a screen, typically inverted relative to the object.

Question 3

In a simple microscope, why is the image formed larger when the object is placed closer to the lens than the focal point?

Accepted Answer

In a simple microscope, placing the object between the lens and focal point results in a virtual, erect, and magnified image. The closer the object is to the lens (inside F), the greater the divergence of rays, increasing the apparent size of the virtual image seen by the observer.

NEET Physics: Ray Optics — Practice Set 17

Q1. An object is at a depth of \( 19.95 \, \text{cm} \) in a medium with refractive index \( 1.5 \). What is the apparent depth?

Q2. Why does a concave mirror form a real image when the object is placed beyond the focal point?

Q3. In a simple microscope, why is the image formed larger when the object is placed closer to the lens than the focal point?

Q4. What is the critical angle for a diamond (\( n = 2.42 \)) to water (\( n = 1.33 \)) interface?

Q5. A concave mirror of focal length \( 7 \, \text{cm} \) has an object placed \( 14 \, \text{cm} \) from it. What is the image distance?

Q6. A convex mirror has a radius of curvature of \( 50 \, \text{cm} \). An object is placed \( 25 \, \text{cm} \) from it. What is the image distance?

Q7. A concave lens of focal length \( 15 \, \text{cm} \) has an object placed \( 30 \, \text{cm} \) from it. What is the image distance?

Q8. A concave lens has a power of \( -2 \, \text{D} \). What is its focal length?

Q9. A concave lens of focal length \( 30 \, \text{cm} \) produces an image \( 15 \, \text{cm} \) from the lens. What is the object distance?

Q10. What optical principle allows a prism to be used as a reflector in optical devices?