Light Flashcards
Give some examples are luminous sources of light
- LED (when on)
- Sun
- Bulb (when on)
- Star
- Firefly
How do we see things that are non-luminous?
We can see them because they reflect light into our eyes
Which of these items in the night sky are luminious?
Mars, Jupiter, galaxies, stars, ISS, Moon, Venus, Comets, Shooting stars
Galaxies
Stars
Shooting stars
How can we see non-luminous items in the night sky?
We can see them as they reflect light from the sun
How fast does light travel?
300 million m/s in air
Light could travel between Belfast and New York in about 100th of a second
How does light travel?
Light travels in straight lines
What is a narrow beam of light called?
A ray
Drawn on a diagram as straight lines with an arrow pointing away from the light source
Describe the image formed by a pinhole camera
The image is inverted
What are two ways the size of the image can be increased in a pinhole camera
- Bring the camera closer
- Longer camera
What is a light year?
The total distance that a beam of light moving in a straight line travels in one year.
Describe transparent
Allows light to travel to straight through
Describe translucent
Lets light through, but scatters it in different directions so we cannot get a clear image
Describe opaque
Does not let light through at all
Why are shadows formed?
- Light rays travel in straight lines
- Some objects are opaque
Shadow forms where light does not reach
Where in a house would translucent glass be useful?
Bathroom for privacy
What is the advantage & disadvantage of using glass for car windscreens
Transparent
Glass is brittle
What happens when an object is moved closer to a light source
The shadow created is bigger.
What happens when an object is moved further away from a light source
The shadow created is smaller
Describe the properties of a shadow
Dark region where no light can reach that takes the shape of the original object.
When does a solar eclipse occur?
When the moon come between the Sun and the Earth.
The shadow of the moon is cast on the Earth
When does a lunar eclispe occur?
Where the Earth blocks some or all of the Sun’s direct light from reaching the moon.
Only takes place during a full moon
What is a transit?
Where a planet appears to move across the surface of a star
When did Venus last transit the sun
5/6th June 2012
when was the last full solar eclipse visible from the UK?
11th August 1999
What is reflection?
Bouncing of light off a surface
What objects are good at reflecting light?
White objects
Shiny objects - these are best as they don’t scatter light in all directions
How does a mirror work?
A mirror reflects all of the light that hits it all in the same direction to produce a clear image.
What is another name for a flat mirror
A plane mirror
What are the differences between a plane and a curved mirror
A plane mirror reflects light to form an image that is the same size at the object
A curved mirror produces images that are a different size than the object
List two ocassions where a curved mirror would be more useful than a plane one
Edge of wing mirrors
Edge of bad-visibility roads
What is the name of the ray coming from the light source (ray box)?
Incident ray
What is the name of the ray bouncing off the mirror?
Reflected ray
What is the normal line when studying reflection?
An imaginary line perpendicular to the mirror
What are the angle of incidence and angle of reflection measured from
They are measured from the normal
What is the law of reflection?
The angle of incidence is equal to the angle of reflection.
What is lateral inversion
The reversal of an image in a mirror e.g. writing RBAI
What are the key features of a periscope?
Object
Mirror
Reflection
2nd mirror
Eye
Look at diagram and being able to label it
What could a periscope be used for?
People controlling a submarine to be able to look about the water.
What is refraction?
The bending of light as it passes through a boundary between two materials of different densities
Why does refraction happen?
It happens because light travels at different speeds in materials of different densities
What happens when light enters a more dense material?
The light waves slow down and bend towards the normal.
What happens when light enters a less dense material?
The light waves speed up and bend away from the normal.
What happens when a ray of light enters a block of perspex at right angles
It travels through the block in a straight line, there is no refraction
What is the splitting of white light into its colours called?
Dispersion
What is the range of colours called when white light is split into its colours
The visible spectrum
What are the 7 colours that white light can get split into
Red
Orange
Yellow
Green
Blue
Indigo
Violet
How is a rainbow formed?
It is formed when sunlight passes through water droplets. The water droplets act as a prism refracting each colour by a different amount to produce the spectrum of light.
What is the full spectrum called when sunlight is split by a prism?
The electronmagnetic spectrum
What are the 7 main areas of the electromagnetic spectrum in order from lowest to highest frequency
- Radio Waves
- Microwaves
- Infrared radiation
- Visible light
- Ultraviolet radiation
- X-rays
- Gamma radiation
Remember My Instructions Visible Using X-Ray Glasses
As frequency increases across the spectrum what happens the wavelength
The wavelength decreases
What type of spectrum is the electormagnetic spectrum?
It is a continuous spectrum, there are no gaps instead there is a type of wave at every wavelength.
What ate the common properties of the electromagnetic spectrum?
- They all travel at the speed of light (300 million m/s)
- They can all travel through a vacuum
- They are all transverse waves
- They transfer energy from one place to another
What is a use and danger of radiowaves?
Use: television & radio
Danger: No known dangers
What is a use and danger of microwaves?
Use: Radar, mobile phone commumications, wireless computer signals, speed cameras, cooking
Dangers: can cause damage to the human body through heating
What is a use and danger of infrared radiation?
Use: Heaters, night-vision, remote controls and in fibre optical communications
Dangers: Too much can cause burns to human skin
What is a use and danger of visible light?
Use: Enables us to see, used by skin to produce vitamin D
Dangers: Too strong a source of light can damage eyes
What is a use and danger of Ultraviolet light?
Use: Fluoresence used in things like washing powder to make clothes look brighter/cleaner. Security marking of valuables/bank notes
Dangers: Can cause skin cancer, damage eyes
What is a use and danger of x-rays?
Use: Taking pictures of bones and teeth, testing welded joins on metal pipes. To kill cancers cells when used in a controlled way in radiotherapy.
Dangers: Can cause cancers by disrupting DNA, can kill cells and can damage a foetus.
What is a use and danger of gamma radiation?
Use: Can kill cancer cells in radiotherapy. Can be used to kill bateria in the sterilsation of hospital equipment. Can be used to preserve food. Gamma cameras can be used to take pictures of tracer fluids to diagnose illness
Dangers: Can damage or kill living cells