The Doppler effect is the apparent change in the frequency or wavelength of a wave (like sound or light) due to the relative motion between the source of the wave and the observer.

6.1.1 The Doppler effect is the apparent change in the frequency or wavelength of a wave (like sound or light) due to the relative motion between the source of the wave and the observer. 6.1.2 a) The constant speed of the car moving towards the stationary sound source is greater than 12 m·s^-1. The observed frequency will INCREASE. b) The sound produced by the source is louder. The observed frequency will REMAIN THE SAME. 6.1.3 Step 1: Calculate the observed frequency (x) in the first scenario. The Doppler effect formula for a moving listener approaching a stationary source is: f_L = f_s ( (v + v_L)/(v) ) Given: • Source frequency f_s = 170 Hz • Speed of sound v = 340 m·s^-1 • Listener speed v_L = 12 m·s^-1 x = 170 Hz ( 340 m·s^-1 + 12 m·s^-1340 m·s^-1 ) x = 170 Hz ( (352)/(340) ) x = 170 Hz × 1.03529 x ≈ 176 Hz Step 2: Calculate the new frequency of the sound source (f_s') in the second scenario. The observed frequency is still x = 176 Hz. The listener now travels towards the stationary sound source at v_L = 24 m·s^-1. The formula is: f_L = f_s' ( (v + v_L)/(v) ) Rearrange to solve for f_s': f_s' = f_L ( (v)/(v + v_L) ) Substitute the values: f_s' = 176 Hz ( 340 m·s^-1340 m·s^-1 + 24 m·s^-1 ) f_s' = 176 Hz ( (340)/(364) ) f_s' = 176 Hz × 0.934065 f_s' ≈ 164.395 Hz The new frequency of the sound source is 164.40 Hz. 6.2 The spectrum that shows the absorption lines of light from another star that is moving AWAY from Earth is Z. Explanation: When a star moves away from Earth, the light it emits undergoes redshift. This means the wavelengths of the absorption lines are shifted towards the red end of the spectrum (longer wavelengths). Compared to the reference spectrum X (from the sun), spectrum Z shows the absorption lines shifted towards the 'R' (red) side, indicating redshift. 3 done, 2 left today. You're making progress.