Physics

The graph shows the relationship between the maximum kinetic energy of emitted photoelectrons and the incident photon energy for four different metal surfaces.

Light of frequency $7 \times 10^{14}\,\mathrm{Hz}$ is incident on the metals.

From which metals are photoelectrons emitted?
A. K, Li only
B. Mg, Ag only
C. All of the metals
D. None of the metals

An absorption spectrum resulting from the passage of visible light from a star’s surface through its hydrogen atmosphere is shown. Absorption lines are labelled W to Z in the diagram.
Determine the surface temperature of the star.

Many scientists have performed experiments to explore the interaction of light and matter.

Analyse how evidence from at least THREE such experiments has contributed to our understanding of physics.

Students plotted the radiation of stars against their wavelengths.

If a star has a surface temperature of $4000\ \mathrm{K}$, what is the maximum wavelength of the radiation emitted by the star?
(A) $0.725 \times 10^{-7}\ \mathrm{m}$
(B) $7.25 \times 10^{-6}\ \mathrm{m}$
(C) $725 \times 10^{-7}\ \mathrm{m}$
(D) $725\ \mathrm{nm}$