Refraction Through a Prism MCQs

Q1. The deviation of light by a prism is least for which colour?

• A.blue
• B.violet
• C.green
• D.red

Answer: D. red

Eliminate first - option A) 'blue' misses the point - Blue deviates more than red; option B) 'violet' fails since Violet deviates the most, not the least; option C) 'green' misses the point - Red, with the longest wavelength, deviates least. That leaves only option D). Confirm with the chapter rule: Red light deviates least through a prism (violet most) (physics, chapter 'The Human Eye and the Colourful World'). Answer: D) red.

Q2. Consider the following statements about refraction through a prism: (I) Light bends towards the base of a prism. (II) Refraction occurs at two surfaces of a prism. (III) The emergent ray is parallel to the incident ray. Which of the above statement(s) is/are correct?

• A.Only III
• B.None of these
• C.Only I
• D.Only I and II

Answer: D. Only I and II

Which principle settles this? Correct: I, II. Does that line up with one of the options? Yes - Correct. And the rest? option A) 'Only III' is wrong because Re-check each statement individually; option B) 'None of these' doesn't hold - Re-check each statement individually. Pick: D) Only I and II.

Q3. While a physics teacher clamps a triangular glass prism on the demonstration bench, a ray strikes one face at 35 degrees and leaves the far face at 40 degrees, the apex angle being 60 degrees. Through what total angle is the ray turned?

• A.5 degrees
• B.65 degrees
• C.15 degrees
• D.135 degrees

Answer: C. 15 degrees

Deviation in a prism follows D = i + e - A = 35 + 40 - 60 = 15 degrees.