Past papers- 6. space physics

Question 1

Explain what is meant by redshift.

State the quantity that the redshift of a galaxy is used to calculate.

Answer 1

wavelength (of light from distant galaxies) increases
occurs when galaxies are moving away (from Earth)

speed / velocity (that galaxy is moving away from Earth)

Question 2

Point X is the point in the orbit closest to the Sun and point Y is the point furthest away. The orbital speed of Pluto varies as it orbits the Sun.

Describe how the speed of Pluto varies as it moves from X to Y and then back to X.

Answer 2

(speed) decreases (from X to Y) and then increases (from Y to X)

 gravitational (potential) energy (GPE) transfers to kinetic energy (KE) or vice versa
 KE transfers to GPE from X to Y AND GPE transfers to KE from Y to X
 speed decreases as KE decreases / ORA
 most GPE at Y OR least GPE at X
 total (of GPE + KE) energy is constant

Question 3

As Pluto rotates, the white surface
alternately faces towards and away from the Sun

Explain how this affects the temperature of Pluto as it rotates on its own axis.

Answer 3

(white surface) is a poor absorber / good reflector / poor emitter of IR / radiation
OR black / other surface is a good absorber / poor reflector / good emitter of IR / radiation

any one from:
(the white surface) increases in temperature less when facing the Sun
(the white surface) decreases in temperature less when facing away (from Sun)
the black / other surfaces increases in temperature more when facing the Sun
the black / other surface decreases in temperature more when facing away (from Sun)
less variation in temperature on white surface (during one whole rotation)