# Physics Unit 1

Unit 1 Revision Notes

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## Electromagnetic waves

The Electromagnetic Spectrum shows that waves have different wavelengths and frequency.

SHORT WAVELENGTH <---> LONG WAVELENGTH

(GAMMA RAYS, X-RAYS, ULTRAVIOLET, VISIBLE LIGHT, INFRARED, MICROWAVES, RADIO WAVES)

HIGH FREQUENCY <---> LOW FREQUENCY

EQUATION TO CALCULATE WAVELENGTH OR FREQUENCY

V = F X λ (WAVE SPEED (IN m/s) X FREQUENCY (IN Hz) = WAVELENGTH (IN m)

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## Electromagnetic waves

The Expanding Universe

RED SHIFT - "The displacement of waves toward longer wavelengths (the red end of the spectrum) in radiation from distant galaxies."

BLUE SHIFT - "The displacement of the spectrum to shorter wavelengths in the light from distant celestial objects moving toward the observer."

The Doppler Effect - "An increase (or decrease) in the frequency of sound, light, or other waves as the source and observer move toward (or away from) each other." eg. When an ambulance with a siren comes towards you and you hear the sound better and then the ambulance moves away.

Red Shift provides evidence that the universe is expanding. Blue Shift gives evidence that the galaxy is moving towards us.

The Big Bang - The theory that the universe started with a massive explosion from a very small point. The earth has been expanding ever since the Big Bang. Cosmic Microwave Background Radiation was created just after the Big Bang.

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## Electromagnetic waves Questions

1. Which part of the electromagnetic spectrum has the longest wavelengths?

2. The wave speed for all electromagnetic waves is 300,000,000 m/s. What is the frequency of electromagnetic waves with a wavelength of 300m? (Velocity / Wavelength)

3. Which part of the electromagnetic spectrum transfers the least energy?

4.  Which part of the electromagnetic spectrum is used to transmit signals to and from satellites?

5. How does visible light travel along an optical fibre?

6. What is the Doppler effect?

7. What is a galaxy?

8. How can we tell that the light from a distant galaxy has been red-shifted?

9. What is the Big Bang Theory?

10. What piece of evidence can only be explained by the Big Bang Theory?

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2. 1,000,000 Hz

4. Microwaves

5. Internal Reflection

6. When there is a change in frequency of waves in a moving source

7. A very large collection of stars

8. By observing the position of dark lines in the spectrum from the galaxy

9. The theory that the universe began with a massive explosion from a small initial point

10. The existence of cosmic microwave background radiation

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This is brilliant, especially for AQA GCSE CORE Science. If you are stuck on the waves topic and need some quick help, use these revision cards. Some quick notes and then questions and answers for you to practice.

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