When a metal plate is exposed to a monochromatic beam of light of wavelength 400nm, a negative potential of 1.1 V is needed to stop the photocurrent . Find the threshold wavelength for the metal.

Explanation

To find the threshold wavelength for the metal, we will use the Einstein photoelectric equation and the relationship between stopping potential and maximum kinetic energy. Here’s a step-by-step solution:

### Step 1: Understand the given data
- Wavelength of the incident light, \( \lambda = 400 \, \text{nm} = 400 \times 10^{-9} \, \text{m} \)
- Stopping potential, \( V_0 = 1.1 \, \text{V} \)

### Step 2: Use the Einstein photoelectric equation
The Einstein photoelectric equation is given by:
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