Question

Which of the following colours of visible light has lowest energy?

• A. Violet
• B. Blue
• C. Yellow
• D. Red

Hint:

Energy of a photon is proportional to frequency, so look for the longest wavelength in the visible range.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The energy of a photon is \(E = h\nu = \frac{hc}{\lambda}\). Energy is directly proportional to frequency and inversely proportional to wavelength.

Step 2: Key Formula or Approach:
Visible light runs from violet (about \(400\) nm) to red (about \(700\) nm). The colour with the longest wavelength has the lowest frequency and so the lowest energy.

Step 3: Detailed Explanation:
Order of wavelength: violet < blue < yellow < red.
So the order of energy is: violet > blue > yellow > red.
Violet and blue have short wavelengths and high frequencies, so they carry more energy per photon. Yellow sits in the middle of the spectrum. Red has the longest wavelength of the four, about \(650-700\) nm, so its photons carry the least energy.

Final Answer:
Red light has the lowest energy among the given colours, option (D). \[ \boxed{\text{Red}} \]