Question

Light of which of the following colours will have the maximum energy in a photon associated with it?

• A. Red light
• B. Yellow light
• C. Green light
• D. Blue light

Hint:

Remember: \[ E=h\nu=\frac{hc}{\lambda}. \] Higher frequency means higher photon energy, while larger wavelength means lower photon energy.

Answer 1

The Correct Option is D

Concept: According to Planck's quantum theory, the energy of a photon is given by \[ E=h\nu, \] where
• \(h\) is Planck's constant,
• \(\nu\) is the frequency of radiation. Since \[ \nu=\frac{c}{\lambda}, \] the energy can also be written as \[ E=\frac{hc}{\lambda}. \] Thus, photon energy is inversely proportional to wavelength. \[ E\propto \frac{1}{\lambda}. \] Hence, the colour having the smallest wavelength will possess the highest photon energy.

Step 1: Recall the order of visible colours according to wavelength. The visible spectrum follows the order \[ \text{Red} \rightarrow \text{Orange} \rightarrow \text{Yellow} \rightarrow \text{Green} \rightarrow \text{Blue} \rightarrow \text{Violet}. \] As we move from red to violet:
• Wavelength decreases.
• Frequency increases.
• Photon energy increases.

Step 2: Compare the given colours. Among the options: \[ \lambda_{\text{blue}} < \lambda_{\text{green}} < \lambda_{\text{yellow}} < \lambda_{\text{red}}. \] Therefore, \[ E_{\text{blue}} > E_{\text{green}} > E_{\text{yellow}} > E_{\text{red}}. \]

Step 3: Identify the colour having maximum photon energy. Since blue light has the highest frequency among the given options, \[ E=h\nu \] will be maximum for blue light. Thus, \[ \boxed{\text{Blue light}} \] has the maximum photon energy. Hence, the correct answer is \[ \boxed{\text{(D)}} \]