No Longer On Exam Flashcards
What type of spectrum do EM waves form?
A continuous spectrum.
Order the types of EM waves/radiation from lowest to highest frequency
- Radio waves.
- Microwaves.
- Infrared.
- Visible light.
- Ultraviolet.
- X-rays.
- Gamma rays.
How do the speeds to EM waves/radiation differ in a vacuum and in air?
Electromagnetic waves all travel at the same speed in a vacuum and in the air.
What property of waves in different mediums causes refraction?
- Velocity.
- Wave speed is slower in denser materials, causing refraction.
In which direction do waves refract when entering a denser medium?
- When entering a more dense medium, the wave slows down.
- This causes them to bend towards the normal.
- This lead to the angle of refraction being less than the angle of incidence.
What type of waves can be produced by oscillations in an electrical circuit?
Radio waves.
How can radio waves create an alternating current in a circuit?
When radio waves are absorbed, they can create oscillations in a circuit with same frequency as the radio waves creating AC.
Where do gamma rays originate from?
They originate from changes in the nuclei of atoms.
What health effects can ultraviolet waves cause?
- They can cause the skin to age prematurely.
- Increase risk of developing skin cancer.
What health effects can X-rays and gamma rays cause?
- They are ionising radiation so can cause mutations in genes.
- They can lead to increased risk of developing various cancers.
Give 3 practical uses for infrared radiation
- Electrical heaters.
- Cooking food.
- Infrared cameras.
How can infrared be used for cooking food?
Infrared light has frequencies which are absorbed by some chemical bonds. The internal energy of the bonds increases when they absorb infrared light, which causes heating.
Give 2 practical uses for microwave radiation
- Satellite communications.
- Cooking food.
How can microwaves be used for cooking food?
High frequency microwaves have frequencies which are easily absorbed by molecules in food. The internal energy of the molecules increases when they absorb microwaves, which causes heating.
How can microwaves be used for satellite communications?
Microwaves pass easily through the atmosphere, so they can pass between stations on earth and satellites in orbit.
Give 2 practical uses for radio waves
- Television transmission.
- Radio transmission.
Give a practical use for visible light
Fibre optic communications.
What wave phenomenon is used by lenses to form an image?
Refraction.
How does a convex lens form an image?
Parallel rays of light are refracted and brought together at a point known as the principal focus.
What is meant by the focal length of a lens?
The distance from the lens to the principal focus.
What is the difference between the image produced by a convex and a concave lens?
- Convex lenses can produce real or virtual images.
- Concave lenses can only produce virtual images.
Why does magnification not have a unit?
- It is the ratio between image height and object height.
- Ratios do not require units.
What symbol is used to represent a convex lens in a ray diagram?
↕
What symbol is used to represent a concave lens in a ray diagram?
Similar to the convex, but arrows point towards the line.
