The wavelength of light is expressed in

Options

A. metre
B. micron
C. light year
D. angstrom

Explanation

To determine the appropriate unit for expressing the wavelength of light, we can follow these steps:

### Step-by-Step Solution

1. **Understanding Wavelength**:
- Wavelength is the distance between successive peaks (or troughs) of a wave. It is a measure of the length of one complete wave cycle.

2. **Identifying Possible Units**:
- The question provides four options: meter, micron, light year, and angstrom. We need to evaluate each of these units to see if they can be used to express wavelength.

3. **Evaluating Meter**:
- The meter (m) is a standard unit of length in the International System of Units (SI). While it can technically be used to express wavelength, wavelengths of light are typically very small compared to a meter, making it cumbersome to use.

4. **Evaluating Micron**:
- A micron (or micrometer, µm) is equal to \(10^{-6}\) meters. This unit is more suitable than meters for expressing wavelengths of light, but it is still relatively large for the wavelengths of visible light.

5. **Evaluating Light Year**:
- A light year is the distance that light travels in one year, which is approximately \(9.46 \times 10^{15}\) meters. This unit is far too large for expressing wavelengths, as wavelengths of light are on the order of nanometers or angstroms.

6. **Evaluating Angstrom**:
- An angstrom (Å) is equal to \(10^{-10}\) meters. This unit is specifically designed for measuring very small distances, such as atomic and molecular scales, making it ideal for expressing the wavelengths of light.

7. **Conclusion**:
- The most appropriate unit for expressing the wavelength of light is the angstrom. The visible spectrum of light ranges from approximately 4000 to 7000 angstroms.

### Final Answer
The wavelength of light is expressed in **angstroms (Å)**.

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