Mark the correct statements(s):

Options

A. Direction of wave propagation is along the normal to wavefront
B. For a point source of light, the shape of wavefronts can be considered to be plane at very large distance from the source
C. A point source of light is placed at the focus of a thin spherical lens, then the shape of the wavefront for emerged light can be plane
D. The shape of the wavefront for the light incident on a thin spherical lens is plane, the shape of the wavefront corresponding to emergent light would always be spherical

Answer

To solve the question, we need to analyze each statement provided and determine whether it is correct or not. Here’s a step-by-step breakdown:

### Step 1: Analyze Statement 1
**Statement:** The direction of wave propagation is along the normal to the wave front.

**Explanation:**
- The wavefront is an imaginary surface representing points of a wave that are in phase.
- The normal to the wavefront is a line perpendicular to the wavefront.
- Waves propagate in the direction of the normal to the wavefront.

**Conclusion:** This statement is correct.

### Step 2: Analyze Statement 2
**Statement:** For a point source of light, the shape of the wavefront can be considered to be plane at a very large distance from the source.

**Explanation:**
- A point source emits waves in all directions, creating spherical wavefronts.
- As the distance from the source increases, the curvature of the wavefront becomes negligible, and it can be approximated as a plane wavefront.

**Conclusion:** This statement is correct.

### Step 3: Analyze Statement 3
**Statement:** The shape of the wavefront for light incident on a thin spherical lens is plane.

**Explanation:**
- When light rays converge or diverge through a thin lens, the wavefronts can be approximated as plane wavefronts after passing through the lens, especially at the focal point.

**Conclusion:** This statement is correct.

### Step 4: Analyze Statement 4
**Statement:** The shape of the wavefront for light emerging from the focus of a thin spherical lens can be plane.

**Explanation:**
- Light that converges at the focus of a thin lens can be considered to emerge as plane waves after passing through the lens, particularly at the focal point.

**Conclusion:** This statement is correct.

### Final Conclusion
All four statements are correct. Therefore, the answer is that statements 1, 2, 3, and 4 are correct.

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