Question

Which of the following is correct for light diverging from a point source?

• A. The intensity decreases in proportion for the distance squared
• B. The wave front is parabolic
• C. The intensity at the wavelength does not depend on the distance
• D. None of these

Answer 1

The correct option is A

The intensity decreases in proportion for the distance squared

Explanation for correct option :

1. A point source generates a spherical wave front that travels in all directions. The intensity is proportional to the distance and follows the inverse square law. As intensity is inversely proportional to distance square.
2. As a result, as the distance from the source increases, the intensity diminishes.

Explanation for incorrect options:

B: The wave front is parabolic

1. A point source does not form a parabolic wavefront. It always forms a spherical wavefront.

C: The intensity at the wavelength does not depend on the distance

1. Intensity is inversely proportional to the fourth power of wavelength which depends on distance.

Hence, the correct answer is option (A).