In Physics, a wave is a pattern of disturbance that transfers energy. You may have seen visual interpretations of waves when dealing with sound especially. They tend to look like fluctuating lines as seen below.
|
There are two types of waves that we'll look at.
The example on the left is an example of a transverse wave. We can judge the "strength", if you like, of the wave by the height (we'll look more at the terminology in a moment) but with a longitudinal wave, this is judged by compression (so how close the waves are together). |
Here is a YouTube video made by "Animations for Physics and Astronomy" to quickly show the difference between Longitudinal and Transverse waves. Link to channel- https://www.youtube.com/channel/UCujISSgt4k4A1AwkoXcqXvA
Transverse Waves-Vibrate at 90 degrees to the direction of energy transfer |
Longitudinal Waves-Vibrate parallel to the direction of energy transfer |
|
|
|
|
|
Value |
|
|
|
Value |
|
The electromagnetic spectrum is a range of wavelengths that have varying types of radiation. The spectrum goes:
Chances are you've already heard the majority of these words before but you can remember them (and in the specific order they come in) with the mnemonic:
- Radio
- Microwave
- Infrared
- Visible
- Ultraviolet
- X-ray
- Gamma
Chances are you've already heard the majority of these words before but you can remember them (and in the specific order they come in) with the mnemonic:
Sound wave experiments
Experiment 1: Oscilloscope/Data logger
This experiment involves placing 2 microphones 1 metre apart from each other and connecting them to an oscilloscope which shows a digital image of the wave. You then make a sound at 1 end and as the sound is picked up by the microphone, a spike will appear on the oscilloscope. When this same sound is picked up by the second microphone another spike will appear on the oscilloscope. then, you have to measure the time difference between the crests of both waves and do distance (1 m)/time to get the speed of sound (343m/s). The same can also be done with a data logger but it will measure the time period for you
Experiment 2: The clap experiment:
In this experiment you stand 100m away from a wall and make a sound 10 times. You make the next sound after you hear the echo of the previous one once it has bounced off the wall. You also need a timer to time the time it takes for you to hear 10 sound echoes. Then you do the time it took for 10 echoes/10 and do distance (100 m)/time to get the speed of sound (343 m/s)
This experiment involves placing 2 microphones 1 metre apart from each other and connecting them to an oscilloscope which shows a digital image of the wave. You then make a sound at 1 end and as the sound is picked up by the microphone, a spike will appear on the oscilloscope. When this same sound is picked up by the second microphone another spike will appear on the oscilloscope. then, you have to measure the time difference between the crests of both waves and do distance (1 m)/time to get the speed of sound (343m/s). The same can also be done with a data logger but it will measure the time period for you
Experiment 2: The clap experiment:
In this experiment you stand 100m away from a wall and make a sound 10 times. You make the next sound after you hear the echo of the previous one once it has bounced off the wall. You also need a timer to time the time it takes for you to hear 10 sound echoes. Then you do the time it took for 10 echoes/10 and do distance (100 m)/time to get the speed of sound (343 m/s)
Refraction
Refraction-When light passes through 2 mediums of different optical density and it bends towards and away from the normal as it enters and exits the mediums of higher and lower optical densities.
Normal-A line that is at 90 degrees to the medium which the light is entering/exiting
Law of reflection/refraction-<i=<r (angle of incidence=angle of reflection/refraction)
Angle of incidence-The angle at which light enters a material of different optical density (<i is the same as the angle at which light exits if it enters the same medium as in which it started) or the angle at which light hits a reflective material
Angle of refraction-The angle between a normal (where the light enters) and a refracted ray
Angle of reflection: The angle between the normal (90 degrees to the mirror) and the reflected ray
Refraction through a cuboid:
When light enters the cube of higher optical density at the <i (angle of incidence) it slows down and bends towards the normal
When it reaches air again, the light bends away from the normal at the <i and ends up parallel to the beam that entered the cube. Also, since the at which the beam enters and exits is the same, if you were to shine the light in the reverse direction, the result would be the same.
Refraction through a semi-circle:
Here, it is very similar to the cuboid but an effect called Total Internal Reflection (TIR) may occur. This is when the angle of incidence passes the critical angle (The angle at which light exits along the boundary of an object) which is around 45 degrees for a semi-circle which means that the light is reflected inside the actual object and the exits at an entirely different angle
Normal-A line that is at 90 degrees to the medium which the light is entering/exiting
Law of reflection/refraction-<i=<r (angle of incidence=angle of reflection/refraction)
Angle of incidence-The angle at which light enters a material of different optical density (<i is the same as the angle at which light exits if it enters the same medium as in which it started) or the angle at which light hits a reflective material
Angle of refraction-The angle between a normal (where the light enters) and a refracted ray
Angle of reflection: The angle between the normal (90 degrees to the mirror) and the reflected ray
Refraction through a cuboid:
When light enters the cube of higher optical density at the <i (angle of incidence) it slows down and bends towards the normal
When it reaches air again, the light bends away from the normal at the <i and ends up parallel to the beam that entered the cube. Also, since the at which the beam enters and exits is the same, if you were to shine the light in the reverse direction, the result would be the same.
Refraction through a semi-circle:
Here, it is very similar to the cuboid but an effect called Total Internal Reflection (TIR) may occur. This is when the angle of incidence passes the critical angle (The angle at which light exits along the boundary of an object) which is around 45 degrees for a semi-circle which means that the light is reflected inside the actual object and the exits at an entirely different angle
Important Equations:
Wave speed=frequency*wavelength
v=fl
Angle of incidence=Angle of reflection/refraction
<i=<r
v=fl
Angle of incidence=Angle of reflection/refraction
<i=<r