1.5 Waves for Communication and Evidence that the Univers is Expanding Flashcards
Which letter represents the wavelength?
a
Which letter represents the amplitude?
b
What type of wave is this?
Transverse
What type of wave is this?
Longitudinal
What type of waves are the electromagnetic waves?
Transverse
What type of waves are sound waves?
Longitudinal
Which electromagnetic wave is fastest in a vacuum?
They are all the same speed
What happens to a wave when it hits an uneven surface?
It reflects at random angles
What happens to a wave when it hits an even surface?
It reflects at the same angle
What is the law of reflection?
Angle of incidence = Angle of reflection
What is refraction?
When a wave crosses a boundary between 2 media and it changes direction because it changes speed
Why do waves refract?
Because the different media have different densities causing the wave to slow down or speed up. This changes the direction
What is diffraction?
Waves spreading out when they pass through a gap or pass an obstacle
What determines the amount of diffraction?
The size of the gap relative to the wavelength of the wave. The narrower the gap/longer the wavelength, the greater diffraction
When does maximun diffraction occur?
When the size of the gap is equal to the size of the wavelength
What are the electromagnetic waves
- Radio waves
- Micro waves
- Infra red
- Visible light
- Ultra violet
- X-Rays
- Gamma rays
Which wave in the electromagnetic spectrum has the smallest wavelength?
Gamma waves
Which wave in the electromagnetic spectrum has the highest frequency?
Gamma rays
Which waves in the electromagnetic spectrum are used for communication?
- Radio waves
- Microwaves
- Infrared
- Visible light
What form of communication are radio waves used for and how?
Television and radio. Long-wave radio waves can be transmitted a long way as they diffract around the Earth. Short-wave radio waves are transmitted a long way as they reflect off the ionosphere.
What form of communication are microwaves used for and how?
Satellite communication and mobile phones. Microwaves can pass through the ionosphere. A microwave is sent to a satellite which is then returned to satellite dishes on Earth
What form of communication are infrared waves used for and how?
Remote controls and optical fibres. Remote controls send different patters of infrared which can be interpreted to preform different actions. Optical fibres carry data over long distances very quickly.
What form of communication is visible light used for and how?
Photography. A lens focuses visible light onto a film or sensor.
Can sound waves reflect/refract/diffract?
Reflect and refract
What affects the pitch of a sound?
Frequency. Higher frequency, higher pitch
What affects the volume of a sound?
Amplitude. Greater amplitude, greater volume
Define the Doppler effect
A moving object that is emitting waves will have different waves depending where you are in relation to the object.
If the object is moving towards you, the frequency will be higher and the wavelength will be shorter.
If the object is moving away from you, the frequency will be lower and the wavelength will be longer.
What does red-shift show and how?
That galaxies are moving away from us. The light from other galaxies have slightly lower frequencies (they’re shifted to the red end of the spectrum), this shows that they’re moving away from us because the doppler of the doppler effect (objects moving away from us have lower frequencies and higher wavelengths)
