Light of wavelength `7200Å` in air has a wavelength in glass `(mu=1.5)` equal to:

Options

A. `7200 Å`
B. `4800 Å`
C. `10800 Å`
D. `6000 Å`

Answer

To find the wavelength of light in glass when given its wavelength in air and the refractive index of glass, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the relationship between wavelength and refractive index**:
The refractive index (μ) of a medium is defined as the ratio of the speed of light in vacuum (or air) to the speed of light in that medium. It can also be expressed in terms of wavelength:
\[ \mu = \frac{\text{Wavelength in air}}{\text{Wavelength in medium}} \]

2. **Rearrange the formula**:
From the above relationship, we can rearrange the formula to find the wavelength in the medium (glass):
\[ \text{Wavelength in glass} = \frac{\text{Wavelength in air}}{\mu} \]

3. **Substitute the known values**:
We know:
- Wavelength in air = 7200 Å
- Refractive index of glass (μ) = 1.5

Substituting these values into the equation gives:
\[ \text{Wavelength in glass} = \frac{7200 \, \text{Å}}{1.5} \]

4. **Perform the calculation**:
Now, we calculate the wavelength in glass:
\[ \text{Wavelength in glass} = \frac{7200}{1.5} = 4800 \, \text{Å} \]

5. **Conclusion**:
Therefore, the wavelength of light in glass is 4800 Å.

### Final Answer:
The wavelength of light in glass is **4800 Å**.

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