Topic 2 - Waves and the Electromagnetic Spectrum Flashcards
(40 cards)
What is a transverse wave?
A wave with sideways vibrations
What is a longitudinal wave?
A wave with parallel vibrations
How can you measure the speed of sound?
By using an oscilloscope
Devise an experiment to measure the speed of water ripples, and thus wave length:
- Place a strobe light above a ripple tank
- This will cast a shadow of waves below
- Time how many waves pass a point in 10 seconds
- Plug results into v = fλ to get the wavelength by rearranging
What 4 things can a wave be when it crosses a boundary?
- Absorbed
- Transmitted
- Reflected
- Refracted
What is refraction?
The changing path of a wave as it moves across a boundary
Why does a wave refract towards the normal when moving into a denser material?
Because one side hits the boundary first (on the inside), causing this to slow down. The other end is still moving fast and hits the boundary later, causing a refraction towards the normal line
What does sound travel as?
A wave
When do we hear a sound?
When our eardrum vibrates
How does our ear interpret sound waves?
- Sound waves cause the eardrum to vibrate
- These vibrations are passed on to tiny bones called ossicles, through the semicircular canals and to the cochlea
- Cochlea turns vibration into electrical signals
- Brain interprets these signals
What is ultrasound?
Sound with frequencies higher than 20000Hz
Give 2 uses of ultrasound waves:
- Medical imaging (pre-natal foetus scans)
- Industrial imaging (finding flaws in materials)
What is infrasound?
Sound with frequencies less than 20Hz
What do earthquakes and explosions create?
Seismic waves
What are the two types of seismic wave?
- P-Wave
- S-Wave
What are the differences between a P-Wave and an S-Wave?
- P-Waves are longitudinal, S-Waves are transverse
- Both pass through solids, but only P-Waves can pass through liquids
- P-Wave are faster than S-Waves
Finish the sentence: For reflection, the angle of incidence is _____ __ the angle of reflection
Equal to
What does total internal reflection depend on?
The critical angle - if the angle of incidence is higher than the critical angle, then total internal reflection occurs
How can you investigate refraction?
- Aim a ray box at a glass box
- Draw a line around the box
- Draw where the line comes into and emerges from the box
- Join up through the box
- Repeat 2-3 times to calculate an average for the angle of incidence
What do colour and transparency depend on?
Absorbed wavelengths
In the visible light range, which colours have the longest and shortest wavelengths?
- Longest = Red
- Shortest = Purple
In the visible light range, which colours have the highest and lowest frequencies?
- Highest = Purple
- Lowest = Red
Finish the sentence: A blue colour filter only lets ____ light pass through it
Blue
What colour would a red hat appear if a blue filter was placed above it?
Black, as the filter does not transmit red, only blue
