In the question number 20, the electromagnetic waves

Options

A. will have same frequency
B. will have a wavelength of 0.3 m
C. fall in the region of radiowaves
D. all of these

Explanation

To solve the problem regarding electromagnetic waves with a given frequency (or gamma) of \( \nu = 10^9 \) Hz, we will follow these steps:

### Step 1: Understand the relationship between wavelength, frequency, and the speed of light.
The relationship between wavelength (\( \lambda \)), frequency (\( \nu \)), and the speed of light (\( c \)) is given by the formula:
\[ \lambda = \frac{c}{\nu} \]
where:
- \( c \) is the speed of light, approximately \( 3 \times 10^8 \) m/s.
- \( \nu \) is the frequency in Hz.

### Step 2: Substitute the values into the formula.
Given:
- \( \nu = 10^9 \) Hz
- \( c = 3 \times 10^8 \) m/s

Substituting these values into the formula:
\[ \lambda = \frac{3 \times 10^8 \text{ m/s}}{10^9 \text{ Hz}} = \frac{3}{10} \text{ m} = 0.3 \text{ m} \]

### Step 3: Analyze the options provided.
1. **First Option**: Same frequency - This is correct as we used \( \nu = 10^9 \) Hz.
2. **Second Option**: Wavelength of 0.3 m - This is correct as we calculated \( \lambda = 0.3 \) m.
3. **Third Option**: Falls in the region of radio waves - Radio waves typically have wavelengths ranging from about 1 mm to 100 km. Since \( 0.3 \) m (or 30 cm) falls within this range, this option is also correct.
4. **Fourth Option**: All of these - Since all previous options are correct, this option is also correct.

### Conclusion:
Since all three options are correct, the answer to the question is:
**All of these options are correct.**