Physics 8.2.1

Question 1

Usually, when an Object Emits Waves, the Wavefronts Spread Out ___.

Answer 1

Symmetrically.

Question 2

If the Wave Source Moves, the Waves Can Become ___, or ___.

Answer 2

Squashed, Stretched.

Question 3

When a Wave-Emitting Object Moves, how will the Wavelengths Change? (2)

Answer 3

-The Wavelength of the Waves In Front of the Source Decrease, & the Frequency Increases.

-The Wavelength Behind the Source Increases, & the Frequency Decreases.

This is Known as the Doppler Effect.

Question 4

The Doppler Effect also Affects ___ Waves.

Answer 4

Light.

Question 5

Explain how the Doppler Effect Affects Light Waves. (2)

Answer 5

-If a Light-Emitting Object Moves Towards an Observer, the Wavelength of Light Decreases.
-This is Called Blueshift, as the Light Moves Towards the Blue End of the Spectrum.

-If a Light-Emitting Object Moves Away From an Observer, the Wavelength of Light Increases.
-This is Called Redshift, as the Light Moves Towards the Red End of the Spectrum.

Question 6

As the Universe Expands, the Distance Between All Bodies is…

Answer 6

Relative.

Question 7

Explain ‘Blue Shift’: (3)

Answer 7

-Blue Shift is when the Wave-Emitting Object is Moving Towards you.

-Wavelength Decreases.

-Frequency Increases.

(Think of Police Sirens).

Question 8

Explain ‘Red Shift’: (3)

Answer 8

-Red Shift is when the Wave-Emitting Object is Moving Away from you.

-Wavelength Increases.

-Frequency Decreases.

(Think of Police Sirens).

Question 9

How Can you Tell that the Universe is Expanding?

Answer 9

Visible Light EM Spectrums from Stars Far Away have the Lines Shifted to the Red End, from where they are on the Visible Light Spectrum of Our Sun. This is Red Shift. Hence, the Star is Moving Away From Us.

Question 10

The Greater the ___ ___ of the Lines on the Visible Light EM Spectrum, the Greater the ___ to the Star.

Answer 10

Red Shift, Distance.