Write three characteristic features in photoelectric effect which cannot be explained on the basis of wave theory of light, but can be explained only using Einstein’s equation.

Explanation

To answer the question regarding the photoelectric effect and its characteristics that cannot be explained by the wave theory of light but can be explained using Einstein's equation, we can follow these steps:

### Step-by-Step Solution:

1. **Introduction to the Photoelectric Effect**:
- The photoelectric effect refers to the phenomenon where electrons are emitted from a material (usually a metal) when it is exposed to light of sufficient frequency. This effect cannot be explained by classical wave theory, which treats light as a continuous wave.

2. **Characteristic Feature 1**:
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