LIGHT, INFRARED, MICROWAVES, AND RADIO WAVES Flashcards
(23 cards)
what is light
light from ordinary lamps and from the Sun
why is it called the white light?
it has all the colours of the visible spectrum in it
what happens to the wavelength of the spectrum?
it increases as you go from violet to red
what do photographers need to know?
how shades and colours of light affect the photographs they take
how does light impact a film camera?
-the light is focused by the camera lens on to a light-sensitive film
-the film then needs to be developed to see the image of the objects that were photographed
how does light affect a digital camera/mobile phone camera?
-the light is focused by the lens on to a sensor, which is made up of thousands of tiny light-sensitive cells called pixels
-each of them give a dot image, which can be seen on a small screen at the back of a camera.
-when a photograph is taken the image is stored electronically on a memory card.
what do all objects emit?
infrared radiation
the hotter an object is
the more infrared radiation it emits
what is infrared radiation absorbed by?
your skin which can damage, burn or kill skin cells as it heats up the cells
why do optical fibres in communication systems use infrared radiation instead of visible light?
infrared radiation is absorbed less than visible light in the glass fibres
why do remote control handsets for Tv and video equipment transmit signals carried by infrared radiation?
-when you press a button on the handset it sends out a sequence of infrared impulses
-it’s used because suitable infrared impulses can easily be produced and detected electronically
why are infrared scanners used in medicine?
to detect infrared radiation emitted from hot spots on the body surface as it means the tissue underneath is unhealthy
why are infrared cameras used?
to see people and animals in the dark
infrared radiation is used to heat up objects quickly?
-electric heaters that emit infrared radiation warm rooms quickly
-electric cookers that have halogen hobs heat up food faster than ordinary hobs as they’re designed to emit much more infrared radiation than ordinary hobs
microwaves have a shorter
wavelength than radio waves
why do people use microwaves for communications (satellite TV )?
because they can pass through the atmosphere and reach satellites above earth.
why do microwave ovens heat food faster than ordinary ovens?
This is because electromagnetic radiation directly heats molecules inside your food, rapidly reheating it in minutes or even seconds.
why do people use microwaves for communications (satellite TV )?
-microwaves, with higher frequencies, are less affected by moisture and gases in the Earth’s atmosphere that can absorb or scatter lower-frequency waves. As a result, microwaves can travel to and from satellites with less signal loss,
what are the frequencies of radio waves?
3 Hz to 3,000 GHz
why are radio waves used?
used for communication such as broadcasting television and radio, communications and satellite transmissions.
why can microwaves and radio waves be hazardous?
- because they can penetrate the body and heat up internal parts of the body
how else do people incorporate radio waves in their daily lives?
. Radio and television broadcasting, mobile phones and their base stations, smart meters and satellite communications all produce RF EME.
absorption and emission of infrared radiation:
