Everything Flashcards
Light
Light travels in straight lines. Theses are called rays.
They can be converging, diverging and parallel
Evidence that light travels in straight lines
Pinhole camera Shadows Light streaming through trees Light streaming through water droplets In clouds Light in a laser beam
Pinhole camera
The image is inverted upside down and formed on screen
The phrase we use for light travelling in straight lines is rectilinear propagation
What speed does light travel at
It travels at 300,000,000mls
When are shadows cast
When an opaque object stops light from reaching an area.
Reflection
The angle of incidence equals the angle of reflection.
This is the law of reflection
All angles are measured from the normal
Where is the image on a plain mirror
The image is the same distance behind the mirror as the object is in front
What is apparent depth
Our eye doesn’t know that the light has been refracted when it comes from water into air and so the brain thinks that it has originated from a point closer to the surface
What is the penumbra and umbra
The penumbra is a larger or extended source there is still an umbra
There is an outer region on the screen where all the light can reach. Between is a ring shaped region , partial shadow called the penumbra it is DIM and SHARP.
The umbra is the darker main shadow
What is a solar eclipse
Solar eclipses work like extended source diagrams
What is dispersion
When we shine light into a prism we see the colours of the rainbow are displayed on the screen
These colours are ROYGBIV
Why does a red ball look red
Because the ball aborbs all the colours of the spectrum except red and it is reflected into the eye
When are sounds made
They are made when a object vibrates eg guitar strings, drum skins, vocal chords
What are compressions and rarefractions
Compressions occur when the particles are closest together
Rarefractions occur when the aprticles are furthest apart
Sound
Sound is a longitudinal wave. This means that the direction or vibration is in the same direction as the movement of the wave
There is air inside a bell jar so sound can travel and be heard but what happens if the air is removed
The bell jar and the sound can’t be heard because there is no air inside the bell jar
The particles in a solid are close together what does this mean
This means vibrations are more easily passed form particle to particle and so sound travels fastest in solids, slower in liquids and slowest in gases
Why can sound not travel in a vacuum
Because there are no molecules to pass on the vibrations. Sound is called a mechanical wave
What happens when sound waves hit a solid
They are reflected back from the surface this is called an echo
What is the speed of sound in water
1500mls
What is the sum for working out how far away something is on a ship
Is the ship sends out a wave and it’s gets back in 1 second then it took 0.55
Distance speed x time
1500 x 0.5 = 750m. Time = distance = 35
Speed
What are sound waves an example of
Longitudinal waves, like other waves sound waves move energy sound. Sounds are caused by vibrations. The particles of medium vibrate in the direction of the wave. Sound cannot travel in a vacuum as there are no particles to carry the vibration
What can humans hear
We can hear sound waves with the frequencies in 20HZ to 20KHZ
The ear
The pina, the ear canal, the ear drum, the 3 small bones (stirrup, anvil and hammer), the throat tube connected to your throat and the cochlea(takes nerve messages to your brain).
