The wavelength of X-rays is 0.01 A. Calculate its frequency. State the assumption made, if any.

Answer

To solve the problem of calculating the frequency of X-rays given their wavelength, we can follow these steps:

### Step-by-Step Solution

1. **Identify the Given Wavelength**:
The wavelength of the X-ray is given as \( \lambda = 0.01 \) Å (Angstrom).

2. **Convert Wavelength to Meters**:
Since 1 Å = \( 10^{-10} \) meters, we convert the wavelength:
\[ \lambda = 0.01 \, \text{Å} = 0.01 \times 10^{-10} \, \text{m} = 10^{-12} \, \text{m} \]

3. **Use the Formula for Frequency**:
The frequency \( f \) can be calculated using the formula:
\[ f = \frac{c}{\lambda} \]
where \( c \) is the speed of light.

4. **Substitute the Speed of Light**:
The speed of light \( c \) is approximately \( 3 \times 10^8 \) m/s. Now, substituting the values into the frequency formula:
\[ f = \frac{3 \times 10^8 \, \text{m/s}}{10^{-12} \, \text{m}} \]

5. **Calculate the Frequency**:
When dividing by \( 10^{-12} \), we can rewrite it as multiplying by \( 10^{12} \):
\[ f = 3 \times 10^8 \times 10^{12} = 3 \times 10^{20} \, \text{Hz} \]

6. **State the Assumption**:
The assumption made in this calculation is that X-rays are electromagnetic (EM) waves that travel at the speed of light, \( c = 3 \times 10^8 \) m/s.

### Final Answer
The frequency of the X-ray is \( 3 \times 10^{20} \) Hz.