light & the EM spectrum Flashcards
How are electromagnetic waves defined?
Transverse waves that transfer energy from source to absorber.
All electromagnetic waves …
- are transverse
- can travel through a vacuum
- travel at same speed in a vacuum
The sun emits several types of EM radiation such as…
- visible light (to see)
- infared (heat earth)
- ultraviolet (energy for photosynthesis)
Radiation with higher energy is…
- highly ionising
- harmful to cells & tissues causing cancer
Radiation with lower energy…
- useful for communications
- less harmful to humans
What are the positives & negatives of microwaves?
Used for communications, cook food.
Risk of internal heating since humans contain a lot of water.
What are the positives & negatives of ultraviolet?
Suntanning, detecting forged banknotes.
Can cause severe eye damage, ionising so can kill cells resulting in skin cancer.
What are the positives & negatives of x rays & gamma rays?
Look at bones & structures inside body, sterilize food & medical equipment.
Most ionising, can cause internal damage & cancer.
What colours have the shortest & longest wavelength?
Red, violet.
What happens in the transmitting antenna?
What happens in a receiving aerial?
Charge from alternating current oscillates up & down antenna producing radio waves.
Metal aerial absorbs radio waves creating alternating current.
The denser the substance…
The slower the wave.
What’s the method for refraction?
- Draw around the glass block
- Draw a normal
- Turn on ray box & draw Xs to indicate paths of light rays
- Turn off ray box & remove block
- Join Xs to show light rays
- Measure angles of reflection & refraction
