When orange light falls on a photo sensitive surfaces the photo current begins to flow. The velocity of emitted electrons will be more when surface is hit by

Options

A. A) Red light
B. B) Violet light
C. C) Thermal radiations
D. D) Radio waves

Answer

To solve the question step by step, we need to analyze the relationship between the frequency of light and the energy of emitted electrons in the context of the photoelectric effect.

### Step-by-Step Solution:

1. **Understanding the Question**:
- The question states that when orange light falls on a photosensitive surface, a photo current begins to flow. We need to determine which type of light will cause the emitted electrons to have a higher velocity.

2. **Identify the Relevant Information**:
- The types of light given are:
- Red light
- Violet light
- Thermal radiations
- Radio waves
- We know that the photo current is related to the energy of the emitted electrons, which depends on the frequency of the incident light.

3. **Frequency and Energy Relationship**:
- According to the photoelectric effect, the energy (E) of the emitted electrons is given by the equation:
\[ E = h \nu \]
where \( h \) is Planck's constant and \( \nu \) (nu) is the frequency of the light.
- Higher frequency light results in higher energy photons, which can impart more energy to the electrons, increasing their velocity.

4. **Frequency Ranges of the Given Lights**:
- Orange light has a frequency of approximately 500 terahertz (THz).
- Red light has a frequency range of approximately 400 to 484 THz.
- Violet light has a frequency range of approximately 668 to 709 THz.
- Thermal radiation has a frequency range of about 3 THz.
- Radio waves have a frequency range of about 3 gigahertz (GHz), which is much lower than the others.

5. **Comparison of Frequencies**:
- Comparing the frequencies:
- Red light < Orange light < Violet light
- Thermal radiation and Radio waves have much lower frequencies than orange light.
- Since violet light has a higher frequency than orange light, it will provide more energy to the emitted electrons.

6. **Conclusion**:
- Therefore, when the surface is hit by violet light, the velocity of the emitted electrons will be more than when it is hit by orange light or any of the other options provided.
- The correct answer is **Option B: Violet light**.