Waves And Electricity Flashcards
Longitudinal waves means
waves in which the medium vibrates/oscillates in the same direction the wave travel in
Transverse waves meaning
Waves in which the medium vibrates/oscillates perpendicular to the direction the wave travels in
Frequency meaning
The number of vibrations passing each second. The speed of the vibrations making the wave
Amplitude meaning
The size of the vibrations. Distance between the equilibrium position and the maximum displacement
Absorb meaning
Energy of a wave is taken into the object they hit.
Wavelength meaning
Distance over which 1 complete
vibration/oscillation/wave cycle happens.
Wavespeed meaning
The speed that a wave propogates (moves away from its source)
What is the trough of a wave?
The lowest point on a wave
What is the peak of a wave?
The highest point of a wave
What is the amplitude of a wave
From peak or trough to the middle
Examples of Longitudinal waves
Sound, P – seismic,
Pressure, Shock, slinky
Examples of transverse waves
Light, Water, S – seismic, slinky, rope, Electromagnetic radiation (Radio, Micro, IR, visible light, UV, X, Gamma)
In a transverse wave what is the direction of vibrations
Up and down
In a longitudinal wave what is the direction of vibration
Side to side
What are waves a method for
Transferring energy
What are waves
A moving disturbance / oscillation / vibration
about a fixed equilibrium point
Similarity’s between light and sound
Both travel as waves (they can reflect and refract),
– both are made by vibrations,
– both can transfer energy and information
Differences between light and sound
– Light is much faster,
– sound is vibrations of particles (so sound cannot travel in a vacuum),
– light is vibrations of electric and magnetic fields (hence its an electromagnetic wave).
How to make shadows
Light travels in straight lines.
Opaque objects do not allow light to travel through them.
When light is shone on an opaque object a shadow forms behind it where the light cannot reach.
Why does a banana look yellow
A banana looks yellow because it reflects yellow light into our eyes and absorbs all other colours.
Why do black objects look black
they do not reflect any colours
Why do white objects look white
they reflect all of the colours of light
Red+green light=
Yellow light
Red+blue light=
Magenta light
Blue+green light=
Cyan light
Red+blue+green light=
White light
What do filters do?
Filters will only transmit (allow to pass through) certain colours of light (parts of the visible light spectrum)
What happens when you use two primary colour filters?
2 primary coloured filters will let no light through
What happens to the three primary colours (red, green and blue) when they pass through a coloured filter?
For a red filter, red light is transmitted, blue and green light is
absorbed
What happens when you put white light through two filters?
Because each filter absorbs two colours of light, all three colours are absorbed.
What happens when you shine white light on different coloured paper and why?
Red paper reflects red light, but absorbs the other colours
What happens when you shine coloured light on different coloured paper and why?
When red or green light is shone onto blue paper, the blue paper absorbs the red light and it appears dark.
When blue light is shone onto blue paper, it reflects the blue light, so when we look at it, it appears to be blue
EXTENSION: WHAT HAPPENS WHEN WHITE LIGHT SHINES ON A MAGENTA SURFACE?
When white light shines on a magenta surface, the blue and red parts of the light are reflected, and the green part is absorbed
What happens when light travels through different materials?
When light travels in different materials its speed will change.
This can make it change direction.
We call this change in of speed (and possibly direction) ‘refraction’.
Dispersion meaning
Dispersion: Different colours are slowed down by different amounts…
which causes them to refract (bend) by different amounts.
This causes them to spread out.
Order of colours
Bending the least :red
Orange
Yellow
Green
Blue
Indigo
Bending the most:violet
How are rainbows made?
The light from the sun is dispersed when it enters each raindrop
The colours are reflected from the back of the raindrop
How do we hear sound
1.Sound waves are collected by the ear lobe or pinna.
2.The waves travel along the ear canal.
The waves make the ear drum vibrate.
The small bones (ossicles) amplify the vibrations
The cochlea turns these into electrical signals
The auditory nerve takes the signals to the brain
