Question

The wavelength of visible light for the green color is 600 𝑛𝑚. The energy of photons of this color is _______ 𝑒𝑉 (rounded off to one decimal place). (Planck’s constant = $6.63 × 10^{−34} 𝐽𝑠, 1 𝑒𝑉 = 1.6 × 10^{−19} 𝐽$, speed of light = $3 × 10^8 𝑚𝑠^{−1}$)

Answer 1

Correct Answer: 2.2

Using the energy formula:

\( E = \frac{h \cdot c}{\lambda}, \)

substitute \(h = 6.63 \times 10^{-34}\), \(c = 3 \times 10^8\), and \(\lambda = 600 \text{ nm} = 600 \times 10^{-9} \text{ m}\):

\( E = \frac{6.63 \times 10^{-34} \cdot 3 \times 10^8}{600 \times 10^{-9}} = 3.315 \times 10^{-19} \text{ J}. \)

Convert to electronvolts:

\( E = \frac{3.315 \times 10^{-19}}{1.6 \times 10^{-19}} = 2.07 \text{ eV}. \)