Showing posts with label P3 Waves. Show all posts
Showing posts with label P3 Waves. Show all posts
Friday, March 17, 2017
Thursday, February 2, 2017
3.32 Relating volume (loudness) of a sound to the amplitude
A higher amplitude produces a louder sound. A lower amplitude produces a quieter sound.
The second will be twice as loud as the amplitude is twice as big.
3.31 Relating pitch of a sound to the frequency
Higher frequency produces higher pitch and lower frequencies produce a lower pitch.
3.30 Investigation to determine frequency of a sound wave using an oscilloscope
Use a microphone and attach it to an oscilloscope. Input a sound in the microphone like let somebody sing a note.
Count the number of wave cycle that note produces in 1 second. That will be the frequency of your sound wave.
Similarly, experiment with different musical notes.
3.29 How an oscilloscope can be used to look at sound waves
A microphone will convert sound signals into electric signals which then can be displayed in a wave form by the oscilloscope. We can use the graph to investigate the amplitude and frequency of the sound that as entering the microphone.
3.28 Methods to to measure speed of sound in air
Visible loud event
- Get 2 people who will be standing 200 to 300 metres apart in a large open space as such they can see each other.
- One person will be responsible for creating a visible loud event like banging a drum.
- The other person will time the difference between seeing that event and hearing that event using a stopwatch.
- Repeat this 3 times and average out the time it takes the sound the travel 200 metres.
- Use the formula speed = distance/time to calculate the speed of sound in air
3.27 Range of human hearing
Humans can hear sounds from 20hz to 20,000hz. The higher frequencies starts to get inaudible as humans get older.
3.26 Reflection, refraction and diffraction of sound waves
Just like light waves sound waves can be reflected, refracted and diffracted.
Sound waves reflect when they hit a large object like a wall. They bounce back and can be heard as echoes.
Sound waves can be refracted when they emeter a different medium. This causes them to bend slightly. When sound waves enter a denser material, they travel faster hence making the angle of refraction greater than the angle of incidence.
Sound waves can be diffracted when the pass a doorway or there as an obstacle in their way. They bend, enabling us to hear sound waves even if there is an obstacle between us and the sound source.
3.25 How digital signal carry more information
They have a larger bandwidth compared to analogue signals.
3.24 Advantage of using digital signal
Digital signal can carry more information per unit of time and they can better maintain their quality of information as it easier to amplify and remove noise.
3.23 Digital vs Analogue signal
Digital signals are pulses with only 2 states on and off. They represent binary bits, 1 and 0.
Analogue signal can vary greatly in amplitude and frequency as they are continuous.
3.22 Relationship between critical angle and refractive index
Sine of critical angle = 1/refractive index
Sin(C) = 1/n
n = 1/sin(C)
3.21 The definition of critical angle
Critical angle = c
Critical angle is the angle of incidence at which the angle of refraction is equal to 90°.
3.20 Role of total internal reflection in transmitting data through optic fibers
Total internal reflection is when, the angle of incidence is greater than the critical angle so that light does not escape a glass prism.
Optic fibers can carry light signals over long distances because the light inside theme bounces around and does not escape.
To draw this make sure that you are applying the law of reflection so that the angle of incidence is visually (no need to measure just approx) same as the angle of reflection.
3.19 Investigation to find refractive index of a glass block
Do the investigation in 3.17 to find the angle of incidence and the angle of refraction. Repeat it 3 times each time shine the light from a slightly different angle and place.
Average out the values for r and i and find the refractive index using the formula
n = sin(i)/sin(r)
3.18 Refractive index
Refractive index = sin of angle of incidence/sine of angle of refraction
n = sin(i)/sin(r)
All of these are angles so no units.
n does not have any units because it is a ratio
n is always greater than 1
3.17 Investigate refraction of light
Refraction of light is when a light wave travelling changes direction because it enters a material with a different opacity than the previous one.
To perform the investigation
- Take a ray box and place it on a sheet of paper
- Place a block of glass on the paper as such that the ray can shine through the glass block
- Outline the position of the glass block
- Mark the ray of light entering and exiting the glass block
- Remove the glass block and join the the points where the light intred and exited the glass block
- Draw a normal line on the entrance of the ray and measure the angle of incidence and the angle of refraction
If the light had refracted, the angle of incidence should have been larger than the angle of refraction. i° > r°
3.16 Construction a ray diagram for the formation of a virtual image on a plane mirror
The object can just be a dot. Make sure the angle of incidence is equal to the angle of reflection.
3.15 The law of reflection
From the normal line, the angle of incidence is same as the angle reflection.
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