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 given its wavelength in air and the refractive index of glass, we can use the following relationship:

\[ \lambda_{medium} = \frac{\lambda_{air}}{\mu} \]

Where:
- \(\lambda_{medium}\) is the wavelength in the medium (glass in this case).
- \(\lambda_{air}\) is the wavelength in air.
- \(\mu\) is the refractive index of the medium.

### Step-by-step Solution:

1. **Identify the given values:**
- Wavelength in air, \(\lambda_{air} = 7200 \, \text{Å}\)
- Refractive index of glass, \(\mu = 1.5\)

2. **Apply the formula:**
We will substitute the known values into the formula:
\[ \lambda_{glass} = \frac{\lambda_{air}}{\mu} = \frac{7200 \, \text{Å}}{1.5} \]

3. **Perform the calculation:**
\[ \lambda_{glass} = \frac{7200}{1.5} = 4800 \, \text{Å} \]

4. **Conclusion:**
The wavelength of light in glass is \(4800 \, \text{Å}\).

### Final Answer:
The wavelength of light in glass is \(4800 \, \text{Å}\).

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