Chapter 7 - Light Flashcards
What are the properties of reflection
All types of waves can be reflected
The velocity, freequency, and wavelength of the reflected and incident ray are the same
Waves are in the same medium
What is the principle of reflection
Angle of incidence = angle of reflection
Incident ray, reflect ray, and normal lie in the same plain.
What happens if the gap is bigger in diffraction
The bending effect reduces
What is the normal
A fictious line that is perpendicular to the plain surface.
What are the 3 types of surfaces to reflect on
how much reflection
Rough/curved - diffused reflection
smooth - almost all light is reflected, some is transmitted
Mirror - 100% of the light is transmitted
How does the wave refract thru diff mediums
Rarer to denser - Towards the normal
Denser to rarer - away from the normal
Refractive index formula
speed of light
Speed of light in m1/speed of light in m2
m1 and m2 = medium 1 and medium 2
or
c/v
c = speed of light in vaccum = 3 * 10^8 m/s
v = speed of light in medium 2
What is a spectrum
why is a spectrum formed when light passes through a prism
a range of colours
Dispersion
Properties of a virtual image
Laterally inverted
Distance of object and image from the mirror are the same
Size of object and image are the same
Upright image
Cannot be caught on a screen
What wave fronts do diff light sources give
name the light sources
Extended light source - cylindrical wave fronts
Point light source - spherical wave fronts.
what is a critical angle
angle at which refracted ray is parallel to the surface of material.
what is a principal focus
Principal focus: the point where rays parallel to the principal axis converge with a converging lens.
what is the principal axis
line that goes through optical center, and the 2 foci.
what is the optical centre
the center of the lens
what is the focal length
distance from principle focus and the optical centre.
when is a real image formed
When object is behind F1
when is a virtual image formed
when object is ahead of F1
define refraction of light
Refraction is the bending when light travels from one medium to another due to the change in speed of the ray of light.
what do convex lenses to do light rays
they converge them
properties of images formed in convex lenses
The image is upright and magnified, it is a virtual image.
how does dispersion of light occur
If a beam of white light is passed through a prism it is dispersed into a spectrum.
what is monochromatic light
Monochromatic light is that of a single frequency.
Common features of EM waves
travel through vacuum
travel at the speed of light
are transverse waves
transfer energy
When are EM waves emited
emitted whenever charged particles oscillate or lose energy
Electromagnetic spectrum (organized by increasing wavelength)
Gamma
x-rays
ultraviolet
light
infrared
microwaves
radio waves:
UHF, VHF, short waves, medium waves, long waves
what are VHF and UHF waves
VHF - very high frequency
UHF - ultra high frequency
Infrared radiation and light
how does an object glow when its heated and at what temp
All objects emit some infrared radiation
When an object heats up, it emits more and more infrared and shorter wave lengths.
at 700 degrees - produces shortest possible wavelengths that can be detected- glows red hot
at 1000 - entire spectrum is covered and the object glows white hot
What is flouresense
Materials that absorb ultra violet and convert its energy to visible light and glow.
What are x-rays
their penetration powers
Rays that are given off when fast-moving electron lose energy very quickly.
short wavelength x rays are extremely penetrating
long wavelength x rays are less penetrating
gamma rays
where do they come from
when are they produced
Rays that come from radioactive materials. Produced when the nuclei of unstable atoms break up or lose energy.
properties of image that originate from behind 2f1
Real
Inverted
Diminished (smaller than the object)
Properties of image that originate between 2f1 and f1
Real
inverted
enlarged (larger than the object)
What happens when the object is in between the f1 and the lens
Rays never converge - form a virtual, upright and magnified image
cannot be caught on a screen
Properties of images formed by concave lens
Virtual
Upright
Smaller than object
what happens when the angle of incidence is less than the critical angle
partial reflection, some light is refracted and some light is reflected
what happens when the angle of incidence is greater than the critical angle
total internal reflection occurs
what happens when the angle of incidence is equal to the critical angle
the angle of refraction is 90 degrees and the refracted ray lies on the principal axis
what physics property do optical fibers make use of
what is their medical use of optical fibres
where else are they used
total internal reflection - all rays are reflected no ray is refracted and escaped
medical use: surgery (endoscopy)
other use: telecommunication
what is the speed of light
3x10^8 m/s
name all the types of waves in order in the electromagnetic spectrum
radio waves
microwaves
infrared waves
visible light
ultraviolet
x-ray
gamma ray
which are the broad electromagnetic rays
radio rays
light rays
gamma rays
as we go from gamma to radio waves what increases/decreases
wavelength increases from gamma to radio (radio has highest wavelength)
energy decreases from gamma to radio (gamma has highest energy)
frequency decreases from gamma to radio (gamma has highest freq)
what are all the colours in the visible light spectrum (give acronym)
violet
indigo
blue
green
yellow
orange
red
(VIBGYOR)
as we go from violet to red how does the wavelength, speed and frequency change
wavelength increases (red has highest wavelength)
frequency decreases (violet has highest frequency)
speed increases (red has highest speed)
which waves travel at the same high speed in a vaccum
infra-red waves, microwaves and radio waves
which waves are used to transport television pictures from satellites
microwaves
when drawing reflection images what is important
draw a bisector of the reflected and incident ray
make sure the angle between incident and bisector = reflected and bisector
refractive index formula, critical angle
refractive index = 1/sin critical angle
Describe the harmful effects on people of excessive exposure to electromagnetic radiation
microwaves
infrared
ultraviolet
x rays
gamma rays
microwaves; internal heating of body cells
infrared; skin burns
ultraviolet; damage to surface cells and eyes, leading to skin cancer and eye conditions
X-rays and gamma rays; mutation or damage to cells in the body
Define total internal deflection
Reflection in a more dense material where there is no refracted ray
Describe how optical fibres are used in telecom
Carry telephone calls and internet data
Signals are coded and sent along the fibre as pulses of laser light
What happens in a short sighted
solution
Incoming rays bend inwards too much before they reach the retina
solution: A concave lens placed in front of the eye
(look at diagram on page 157 of tb atl once to get a good idea)
scientific name - myopia
What happens in a long sighted eye
solution
Incoming rays don’t bend inwards enough so when they reach the retina they still haven’t met
solution: a convex lens in placed in front of the eye
(look at diagram on page 157 of tb atl once to get a good idea)
hyperopia
What is a bifocal lens
Top of the lens aid in looking at distant objects
bottom part of the lens - looking at objects that are close
In order to use a convex lens as a magnifying class, where does the object have to be
what kind of image
properties of image
where is the eye
Object between F1 and Lens
Virtual image
Upright
magnified
Cannot be picked up on a screen
Eye - opposite side of the object looking through the diverging rays
Common uses of radio waves
radio and television transmissions
astronomy
radio frequency identification (RFID) - Contactless debit and credit cards contain a tiny chip. When a reader sends out radio waves the chip emits data signals.
Common uses of microwaves
satellite television
mobile phones
microwave ovens
Common uses of infrared waves
electric grills
short range communications such as remote controllers for televisions
intruder alarms
thermal imaging
optical fibres
Common uses of visible light
vision
photography
illumination
Common uses of UV
security marking
detecting fake bank notes
sterilising water
Common uses of Xray
medical scanning
security scanners
Common uses of gamma
sterilising food and medical
equipment
detection of cancer and its
treatment - cheomotherapy
How is communication between satelites possible
types of satellite phones
Microwaves
some satellite phones use low earth orbit (LEO) artificial satellites
some satellite phones and direct broadcast satellite television use geostationary (GEO) satellites
Why do mobile phones and wireless internet use microwaves
microwaves can penetrate some walls and only require a short aerial for transmission and reception
How does Bluetooth make use of EM waves
why? disadv
low energy radio waves or microwaves
they can pass through walls but the signal is weakened on doing so
Which em waves are used in optical fibres
visible light
infrared rays
Define an analogue signal
define a digital signal
Sound waves entering a microphone make its voltage across vary. When this variation is continous it is known as an analogue signal
Digital signal - a signal represented by numbers
2 ways sound can be transmitted
as a digital or analogue signal
benefits of digital signaling
including increased rate of transmission of data
increased range due to accurate signal regeneration
describe one use of optical fibre in medicine
Light travels down (optic) fibres into or out of body
To examine internal organ
Light travels both ways into and out of body
