Waves Flashcards
What is a wave?
A wave is a vibration that transfers energy without transferring matter.
What is the amplitude of a wave?
How tall it is from the normal to the peak.
What is the wavelength of a wave?
The length it takes for the wave to go up, down and return to the normal.
What is the frequency of a wave?
The number of complete waves that pass a point per second.
What is wave frequency measured in?
Hertz
What is 1 Hz equivalent to?
1 wave past a point per second
What is the wave equation?
Speed = Hz x wavelength
Speed = m/s
Frequency = Hz
Wavelength = metres
What are transverse waves?
Waves that vibrate perpendicular to the direction of energy transfer in the wave.
What are four examples of transverse waves?
- Electromagnetic waves
- Ripples on water
- Waves on strings
- Slinky being shaken up and down
What is a longitudinal wave?
A wave in which the vibrations are parallel to the direction of energy transfer.
What are three examples of longitudinal waves?
- Sound and ultrasound
- Seismic Waves
- Slinky being pushed at one end
What are mechanical waves?
Waves that require a medium to travel through so cannot cross vacuums.
What is reflection?
When light bounces off a new medium. It allows us to see.
What kind of a surface provides a clear reflection?
A smooth, shiny surface.
How is a clear reflection formed?
All the light bounces off the medium at the same angle.
What is refraction?
When a wave changes direction as it crosses a boundary between media.
What happens to light travelling along the normal?
It isn’t refracted.
What is diffraction?
When a wave spreads out at the edges when it passes through a gap. The narrower the gap, the more the wave spreads out.
What are three qualities of Electromagnetic waves?
- Vary in wavelength from 10 to the power -15 to 10 to the power 4 metres.
- Travel at the same speed in the vacuum.
- Have higher frequencies as their wavelengths decrease.
Which type of electromagnetic wave has the largest wavelength?
Radio
Which type of electromagnetic wave has the highest frequency?
Gamma
What type of electromagnetic wave has the most energy?
Gamma
What is the main use for radio waves?
Transmission of radio and TV broadcasts.
Why might one use long-wave radio waves?
They have the ability to diffract around obstacles like the Earth’s curvature and hills. As such, the transmitter and the aerial don’t need to be in line.
How are short-wave and medium-wave radio waves transmitted?
They are bounced off the ionosphere.
What is a disadvantage of using short-wave radio waves?
The aerial must be directly in line with the transmitter.
What are three uses of microwaves?
- Communication with satellites
- Satellites make observations
- Mobiles sending messages
What is a potential problem with using microwaves?
They heat our cells and body water which could induce cancer.
What are two uses of infrared waves?
- Remote controls
* Fibre optics
What gives off IR radiation?
Anything that’s hot.
What rule connects an object’s heat and the amount of radiation it gives off?
The hotter the object, the more IR waves it gives off.
What is a use of IR radiation?
Thermal imaging which allows us to see when there’s not enough visible light.
How do cameras work?
They use a lens to focus light onto a photosensitive film or a CCD.
What does a lens do in a camera?
It controls how much light enters the camera.
What does a shutter in a camera do?
Control how long the film/CCD is exposed to light.
How can photographers change exposure in their photos?
Change the amount of light the lens lets in and how long the CCD/film is exposed for.
What is the law of reflection?
i = r
i = angle of incidence
r = angle of reflection
What is an image?
A picture formed by the light from an object.
What is a virtual image?
An image that appears to be coming from one place although the rays of light meet somewhere else.
Give an example of a virtual image.
A mirror image.
What steps are involved in drawing a P1-style Ray diagram?
1) Draw the reflected image.
2) Draw a line between the top of the image and the top of the eye. The part between the image and the mirror should be dotted because it is virtual.
3) Draw an incident Ray from the top of the object to the mirror and then reflected back into the top of the eye.
4) Repeat this process for the bottom of the object.
Why can’t sound waves travel through a vacuum?
Because they are mechanical - they require a medium to travel through.
What kind of surfaces reflects sound waves?
Hard, flat surfaces.
Why is there a delay between a noise and its echo?
Because the sound waves of the echo have the furthest to travel.
What is the relationship between the frequency of a sound wave and its pitch?
The higher the frequency the higher the pitch.
What is the relationship between the amplitude of a wave and its volume?
The bigger the amplitude, the louder the sound.
What is the Doppler effect?
The way that an object that’s moving towards you waves appears to have waves of a shorter wavelength and a an object that moving away from you appears to have waves of a longer wavelength.
What is red shift?
When a light emitting object is moving away from you it appears red as its wavelengths appear to be longer.
What is blue shift?
When a light emitting object is moving towards you it appears red as its wavelengths appear to be shorter.
What are black spots?
Points in the universe where visible light is being totally absorbed.
Why do black spots appear red?
Because they are moving away from us so red shift comes into effect.
What is the big band theory?
The theory that all matter and energy was once compressed into a very small space. It then exploded and forced everything away from that one original point. Red shift helps to prove this because black spots appear red meaning they are moving away from us.
What is the Steady State Theory?
The theory that the universe has always existed as it does now and will forever.
What debunked the Steady State theory?
The discovery of Cosmic Microwave Background Radiation.
What is Cosmic Microwave Background Radiation?
Low-frequency microwave radiation coming from everything in the universe.
What is CMBR attributed to?
Everything cooling down after the Big Bang.
What are three questions that still remain about the Big Bang?
- How did the explosion happen?
- Where did the matter come from?
- What were conditions like before the Big Bang?
