Year 9 Physics - Sound and Light

The Doppler Effect and Sound Intro

• pitch corresponds to frequency, so we can hear 20 - 20,000 Hz
• too high to hear are ultrasounds
• some high or loud sounds can be damaging to our ears
• we use decibels to measure noise, which are logarithmic
• the closer the source, the higher the pitch - the further away the source, the lower the pitch
• this is because the waves emitted before catch up with the sound and increase the frequency of the new waves being emitted

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Light Intro

• light is a type of energy that travels in waves
• any time of energy given off by objects as waves or particles is called radiation, so light is a type of radiation
• light is the only electromagnetic radiation humans can see
• the full range of electromagnetic radiation is called the electromagnetic spectrum
• all electromagnetic waves travel at the speed of light
• electromagnetic waves vary due to their wavelength, as this relates to the amount of energy transferred

  short wavelength - high energy

  long wavelength - low energy

• EMR - shows wave-like properties as it travels through space, and moves in a straight line
• electromagnetic radiation varies both relative to frequency and wavelength

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X-Ray

• shorter wavelength, higher energy
• travels through materials differently - can be used for medical analysis

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Microwave

• longer wavelength and lower energy
• absorbed by certain materials, such as food, which in turn heats it up

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