Question

Assertion (A): When rays of white light pass through a prism, on emerging they give spectrum of seven colours.
Reason (R): It is due to the scattering of light that red light bends minimum and violet light bends the maximum.

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false, but Reason (R) is true.

Hint:

Key differences:

• \textbf{Dispersion:} Splitting of white light into colours due to different bending (refraction) of different wavelengths.
• \textbf{Scattering:} Redirection of light by particles (e.g., blue sky, red sunset).
• In a prism, it's dispersion, not scattering!

Answer 1

The Correct Option is C

Step 1: Analyze Assertion (A).
Assertion (A): "When rays of white light pass through a prism, on emerging they give spectrum of seven colours."

• White light is composed of seven colours: Violet, Indigo, Blue, Green, Yellow, Orange, Red (VIBGYOR).
• When white light passes through a prism, it splits into its constituent colours due to dispersion.
• This phenomenon was demonstrated by Isaac Newton.
• Therefore, Assertion (A) is TRUE.

Step 2: Analyze Reason (R).
Reason (R): "It is due to the scattering of light that red light bends minimum and violet light bends the maximum."

• The splitting of white light into its constituent colours is called dispersion, not scattering.
• Scattering of light is a different phenomenon (e.g., Tyndall effect, blue colour of sky) where light is redirected in different directions by particles.
• The correct reason for dispersion is that different colours of light have different wavelengths and travel at different speeds through the prism material, causing different angles of refraction (bending).
• Red light has the longest wavelength and bends the least, while violet light has the shortest wavelength and bends the most - this is due to refraction and dispersion, not scattering.
• Therefore, Reason (R) is FALSE because it incorrectly attributes the phenomenon to scattering.

Step 3: Check the relationship.

• Assertion (A) is true.
• Reason (R) is false (incorrect terminology - scattering instead of dispersion/refraction).
• Since Reason is false, options (A) and (B) are eliminated.
• Option (C) states "Assertion (A) is true, but Reason (R) is false" which matches our analysis.

Final Answer: (C) Assertion (A) is true, but Reason (R) is false.