Which properties of electromagnetic radiation are inversely related?

$ \textbf{(A)}\ \text{amplitude and frequency} \qquad$
$\textbf{(B)}\ \text{energy and wavelength} \qquad$
$\textbf{(C)}\ \text{energy and frequency} \qquad$
$\textbf{(D)}\ \text{wavelength and amplitude}\qquad$
1. **Amplitude and Frequency**: 
   - Amplitude and frequency are properties of a wave, but they are not directly related to each other. The amplitude of a wave is the height of the wave, while the frequency is the number of cycles per second. There is no inverse relationship between these two properties.
   - Therefore, option (A) is incorrect.

2. **Energy and Wavelength**:
   - The energy \(E\) of a photon is given by the equation \(E = hf\), where \(h\) is Planck's constant and \(f\) is the frequency of the wave.
   - The frequency \(f\) is related to the wavelength \(\lambda\) by the equation \(f = \frac{c}{\lambda}\), where \(c\) is the speed of light.
   - Substituting \(f = \frac{c}{\lambda}\) into the energy equation, we get:
     \[
     E = h \left(\frac{c}{\lambda}\right) = \frac{hc}{\lambda}
     \]
   - This shows that energy \(E\) is inversely proportional to the wavelength \(\lambda\).
   - Therefore, option (B) is correct.

3. **Energy and Frequency**:
   - As mentioned earlier, the energy \(E\) of a photon is given by \(E = hf\).
   - This shows that energy \(E\) is directly proportional to the frequency \(f\), not inversely proportional.
   - Therefore, option (C) is incorrect.

4. **Wavelength and Amplitude**:
   - Wavelength and amplitude are properties of a wave, but they are not directly related to each other. The wavelength is the distance between successive crests of a wave, while the amplitude is the height of the wave.
   - There is no inverse relationship between these two properties.
   - Therefore, option (D) is incorrect.

The final answer is \( \boxed{\textbf{(B)}} \)