Physics Questions Flashcards
Radio waves are part of the electromagnetic spectrum. Suggest a property of radio waves that makes them suitable for use in communication
(Radio waves can) travel quickly; [1 mark]
(Radio waves can) code information (in their frequency); [1 mark]
(Radio waves can) pass through the human body without causing any harm; [1 mark]
(Radio waves can) travel long distances / through objects / through walls (thanks to their large wavelength); [1 mark]
(Radio waves can) diffract / reflect (in hilly terrain); [1 mark]
An ultrasound wave travels faster in the patient than it does in the air. Explain how a change in speed affects the wavelength of the ultrasound wave
How a change in speed affects the wavelength:
Recall the wave equation:
v e l o c i t y space equals space f r e q u e n c y space cross times w a v e l e n g t h
State that frequency is a constant:
Since frequency is the number of oscillations per second it is caused at the source of the wave and does not change; [1 mark]
Evaluate the equation:
Velocity is directly proportional to wavelength OR as speed increases, wavelength increases; [1 mark]
Two students investigate the speed of sound waves in air. They use a stopwatch that shows time to the nearest 0,1s. They use an outdoor running track as their measure of distance. The track is straight and 100 metres long. Describe what else they must do to obtain a value for the speed of sound.
Using a method to make a loud sound (which can be heard 100 m away); [1 mark]
Use of the equation for speed, s equals d over t; [1 mark]
Doing the experiment in still air/where there is no wind/repeating in opposite direction to account for wind speed; [1 mark]
Repeat readings and taking the average/ignore outliers; [1 mark]
Check for zero error on the stopwatch; [1 mark]
Using a clear visual signal to the person starting the stopwatch; [1 mark]
Measure the time between seeing signal and hearing sound; [1 mark]
Take into account reaction time; [1 mark]
Name one type of wave that is used in cancer treatment and explain what it does during the treatment
A wave that is used in cancer treatment:
Gamma-rays; [1 mark]
They ionise cancerous cells, causing them to die; [1 mark]
A ray of light enters a block of glass and is refracted. Explain why the ray of light is refracted towards the normal?
To explain why the ray of light is refracted towards the normal:
Compare the two materials:
The light is travelling from air to glass
Therefore it is passing from a less dense medium to a more dense one
Explain the consequence of moving from less dense to more dense medium:
The refractive index of glass is higher than for air; [1 mark]
The speed will decrease OR the wavelength will increase; [1 mark]
Explain why rays of light inside a diamond are more likely to be totally internally reflected than those inside an opal?
The refractive index of opal is about 1.5. The refractive index of diamond is 4.
To explain why rays of light inside a diamond are more likely to be totally internally reflected than those inside an opal:
Any three points from:
Larger refractive index leads to a smaller critical angle; [1 mark]
Total internal reflection happens when the angle of incidence is larger than the critical angle; [1 mark]
Diamond will have a larger range of possible angles for TIR; [1 mark]
for diamond: sin open parentheses c close parentheses space equals space 1 over n equals 1 fourth equals 0.25 therefore c = 14° [1 mark]
Only angles between 43-90° will cause total internal reflection in opal; [1 mark]
