Question 385: Wave Optics

Question

When a photon enters glass from air, which one of the following quantity does not change?

Accepted Answer

When a photon transitions from air to glass, its velocity, wavelength, and momentum do experience changes due to the optical density and refractive index of the glass, which are different from those of air. However, the energy of the photon does not change upon entering the glass from air. The energy of a photon is given by the equation:
$$E = hf = \frac{hc}{\lambda},$$
where $E$ is the energy of the photon, $h$ is the Planck constant, $f$ is the frequency of the photon, $c$ is the speed of light in a vacuum, and $\lambda$ is the wavelength of the photon in a vacuum. When the photon enters glass from air, its speed and wavelength change, but its frequency, $f$, remains constant, since frequency is determined by the source of the light and is not affected by the medium through which the light is traveling. Since the energy of the photon depends directly on its frequency (and not on its speed or wavelength within the medium), the energy of the photon remains unchanged during the transition. Therefore, the correct option is:
Option D: Energy

Answer

Velocity

Answer

Wavelength

Answer

Momentum

Answer

Energy

Wave Optics

When a photon enters glass from air, which one of the following quantity does not change?

Choose the correct answer: