Question

A point object O is placed in front of a glass rod having spherical end of radius of curvature 30cm. The refractive index of glass is μ = 1.5. The image would be formed at: 

• A. 30 cm left
• B. infinity
• C. 1 cm to the right
• D. 18 cm to the left

Hint:

If the refraction formula gives zero reciprocal image distance, the image is formed at infinity.

Answer 1

The Correct Option is B

Step 1: Refraction at a spherical surface: (mu₂)/(v) - (mu₁)/(u) = (mu₂ - mu₁)/(R)
Step 2: Substitute values: mu₁ = 1, mu₂ = 1.5, u = -15cm, R = 30cm
Step 3: (1.5)/(v) + (1)/(15) = (0.5)/(30) ⟹ (1.5)/(v) = 0
Step 4: v = ∞