In excited H atom when electron drop from `n = 4,5,6` to `n = 1`, there is emission of

Options

A. UV light
B. Visible light
C. IR light
D. Radio waves

Answer

To determine the type of light emitted when an electron in a hydrogen atom transitions from higher energy levels (n = 4, 5, 6) to the ground state (n = 1), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Energy Levels**: In a hydrogen atom, electrons occupy discrete energy levels denoted by the principal quantum number \( n \). The ground state corresponds to \( n = 1 \), and excited states correspond to \( n = 2, 3, 4, 5, \) and \( 6 \).

2. **Identify the Transition**: The question specifies that the electron is dropping from \( n = 4, 5, \) or \( 6 \) to \( n = 1 \). This is a transition from a higher energy level to the lowest energy level.

3. **Calculate the Energy of the Transition**: The energy of the emitted photon during the transition can be calculated using the formula:
\[ E = -13.6 \, \text{eV} \left( \frac{1}{n_1^2} - \frac{1}{n_2^2} \right) \]
where \( n_1 = 1 \) and \( n_2 \) can be \( 4, 5, \) or \( 6 \).

4. **Determine the Wavelength**: The energy of the emitted photon is related to its wavelength (\( \lambda \)) by the equation:
\[ E = \frac{hc}{\lambda} \]
where \( h \) is Planck's constant and \( c \) is the speed of light. By rearranging this equation, we can find the wavelength:
\[ \lambda = \frac{hc}{E} \]

5. **Identify the Region of the Electromagnetic Spectrum**: The wavelength can be used to determine the type of light emitted:
- UV light has wavelengths between approximately 10 nm to 400 nm.
- Visible light has wavelengths between approximately 400 nm to 700 nm.
- Infrared (IR) light has wavelengths longer than 700 nm.
- Radio waves have much longer wavelengths.

6. **Conclusion**: Since the transitions from \( n = 4, 5, 6 \) to \( n = 1 \) result in high energy emissions, the emitted light will fall in the ultraviolet (UV) region of the electromagnetic spectrum.

### Final Answer:
The emission of light when an electron drops from \( n = 4, 5, 6 \) to \( n = 1 \) in an excited hydrogen atom is **UV light**.