1

Write down a formula that relates the wavelength and frequency for a light wave travelling in a vacuum.

Use your formula to determine the wavelength that corresponds to the frequency 1400 THz.

Show all your working, and take care to use units consistently throughout, remembering that 1 Hz = 1 s^-1.

If required, take the speed of light in a vacuum to be c = 3.0 10⁸ m s^-1 2

Calculate the photon energy that corresponds to the frequency 1400 THz.

You should assume Planck's constant h = 6.63 10^?34 J s, use units consistently throughout, and give your final answer to an appropriate number of significant figures.

3

The Hertzsprung-Russell (HR) diagram shown in Figure 3 below represents the main sequence by a curved band of approximately uniform width. As a consequence, at any given value of the surface temperature, the stars in the main sequence represent a range of stellar luminosities relative to the luminosity of the Sun shown as L/LQ. L l LG mam sequence 10 000 6000 3000 surface temperature 1' K Figure 3 The Hertzsprung-Russell diagram Show description V i. Using the HR diagram (Figure 3) what is the approximate range of relative luminosities covered for a main sequence star at 3000 K? (1 mark) ii. Would this star be most like Betelgeuse or Sirius