Physics Light & EM

Question Answer
What happens if sound waves cross the boundary at an agle of 90 degrees? They carry on straight
All angles are measured between light rays and the …… Normal
How is infrared used in astronomy? The universe contains vast amount of dust and infrared telescopes can peer into the hearts of dusty galaxies
What is refraction? Refraction is the change in speed when light rays travel from one medium to another which can lead to a change in direction
What is the focal point? The point in which the light rays meet
Describe how microwaves are used in radar systems Radar works by transmitting a beam of microwaves, detecting the signals reflected back from objects in the path of the beam
What does a convex lens do to light rays? Brings them together to a point
State a practical use of UV radiation Steralizing work places
How do you calculate lambda? v/f
Give 3 examples of communication systems that use microwaves mobile phones, satellite tv and wifi and bluetooth
How do physiotherapists use infrared radiation? They heat damaged tissues to help them heal quicker
How does sun tan lotion work? It absorbs the shorter wavelength UV rays that cause sunburn and allow the longer waves to reach the skin creating a tan
How can you protect yourself from the harmful rays of the sun? Sun-tan lotion
Why is too much exposure to UV rays bad for your health? It can cause skin to burn and become painful
Why is UV radiation needed by the body? To produce Vitamin D3, which allows calcium to be absorbed from our food
Name the EM spectrum
Give an examople of the use of infrared images of earth from space These images can provide an early warning for El Nino events and helo to prevent potential storms
What is a periscope used for? Seeing around or over objects
What happens to parallel rays of light when they strike a concave mirror? The rays will reflect inwards towards a focal point
What happens to parallel rays of light when they strike a convex mirror? The rays will travel directly away from an imaginary focal point
How does the focal length of the lens affect the image that is formed by the lens? The smaller the focal length the smaller the image
What is a lens? A lens is an optical device which refracts light
Describe how radio waves can be produced Naturally occuring radio waves can be produced by lightening. Unntatural radio waves are produced by radio transmitters
How are radio waves? The size of buildings or people
How big are gamma rays? The size of atomic nuclei
What does the whole EM spectrum have in common? Travel at the speed of light
What is a medical use of radio waves Radio waves can produced 3D images of the bodys organs and structures
Give two uses for Xrays Can take images of bones and other body parts such as the brain or lungs
Describe how X-Rays work X-rays are directed at the object to be imaged and some of the Xrays are absorbed as they pass through and then hit a photographic plate on the other side of the object to blacken it
Describe what happens when X-Rays strike a photographic film They are absorbed through the body except where they are absorbed by dense structures like bone
What is a natural source of Gamma Rays Gamma decay
What is irradiation? The process in which an object is exposed to radiation
What type of waves are light waves? Transverse
Give one example of how sound waves are different to light waves? Light waves can travel through a vaccum
What does laterally inverted mean? Letters and words look like they have been written backwards
How does light travel? In straight lines
What is the law of reflection? The angle of incidence is equal to the angle of reflection
What happens when light passes from a fast medium to a slow medium ? It bends towards the normal
What happens when light passes from a slow medium to a fast medium? It bends away from the normal
Give 3 examples where lenses are used Microscopes, cameras, telescopes, projectors
How can the focal length of a concave lens be measured be measured? Placing a lens in front of a screen and moving the lens until a sharp image of a distant object is obtained on the screen, then measuring the distance from the lens to the screen (this is the focal legnth)
How can you correct short sight? A concave lens to spread the rays of light out before they enter the eye
How can you correct long sight? A convex lens to bring the light rays together before entering the eye
What are prisms used for and how does this work? To seperate white light into the spectrum of visible light – ROYGBIV. This works because different wavelegnths of light are refracted by slightly different amounts
What is the electromagnetic spectrum? An oscillation of electrical and magnetic fields that travel through space as a wave and carries energy
How is the electromagnetic spectrum split up? according to its wavelegnth ( or frequency)
How can you detect radio waves? Aerial
How can you detect microwaves? Aerial
How can you detect infrared? thermochromic film
How can you detect visible light? Photographic film
HOw can you detect ultraviolet? Fluorescent chemicals
how can you detect x rays? Photographic film
How can you detect gamma rays? Photographic film
How is ultraviolet radiation used in forensics? For looking at fingerprints
What happens to the focal legnth when you increase the thickness of the lens ? The focal length decreases
What is the scientific word for short and long sighted? Short – myopia . Long – hypermetropia
If you were to put a convex lens in front of a window and a screen behind the lens to produce an image of the window, what 3 things would you notice about this window? Upside down, smaller, back to front
When is the angle of refraction greater than the angle of incidence ? When light leaves a medium as it is bent away from the normal
What is the angle of incidence? The angle between the incident ray and the normal
Which colour is refracted the least and why? Red because the short the wavelegnth of the light, the more it is refracted
What does medium mean? Another word fo material
What is light ? An electromagnetic wave that is visible to the human eye
What is a converging and diversion lens Convex and concave (in order )
What can a short sighted person see Short sighted people can see objects clearly in front of them but struggle to see objects from far awag
What two surfaces are great at absorbing and reflecting infrared radiation? Black and shiny surfaces
What materials can microwaves pass through? Plastic and glass
Why can microwaves not travel through metals? Because metals reflect microwaves
Out of UV A, B and C, which has the higher frequency? UV C
What is the most dangerous type of UV radiation? UV C
What two types of waves make an Amplitude Modulation Wave Audio Signal and Carrier Wave
What are transverse waves? Transverse waves are where the vibrations are at right angles to the direction of travel
What are longitudinal waves? Where the vibrations are in the same direction to the direction of travel
What is amplitude modulation? A technique used to transmit sound information via radio waves
Why are CAT scanners now used instead of X-Rays more? Because they produce much more data and detail
What safety precausions are made when using X rays? Not only are patients limited to the amount of X rays they are allowed to have but hospital staff must wait outside a room with a shielded lead infused wall for max protection
What is diffraction? The bending of waves around obsticles and openings
What is the focal legnth? The distance between the lens and the image sensor when the subject is in focus