Question

Which from following colours has highest energy if wave lengths of violet, blue, yellow and red light are 410 nm, 470 nm, 580 nm and 750 nm respectively ?

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

Hint:

Energy of a photon is inversely proportional to wavelength, so pick the shortest wavelength.

Answer 1

The Correct Option is B

Step 1: Compare photon energies numerically:
Take $E = hc/\lambda$ with $hc \approx 1240$ eV nm.
Violet: $1240/410 \approx 3.02$ eV.
Blue: $1240/470 \approx 2.64$ eV.
Yellow: $1240/580 \approx 2.14$ eV.
Red: $1240/750 \approx 1.65$ eV.

Step 2: Read off the largest:
The largest value is 3.02 eV, which belongs to violet light. The energies fall steadily as the wavelength grows, so blue, yellow and red are each lower.

Step 3: Why the others fail:
A longer wavelength means a lower frequency and so less energy per photon. Blue, yellow and red all have longer wavelengths than violet, so none of them can beat it.

Final Answer:
Violet at 410 nm gives about 3.02 eV, the highest, which is option (B). \[ \boxed{\text{Violet (B)}} \]