Topic 5 Flashcards
Done except for a few specs
5.1P
What is the law of reflection?
<incidence = <reflection.
True for all waves
5.1P
Describe the circumstance needed for total internal reflection to take place
<incidence needs to be greater than <critical
5.1P
What is the critical angle?
Angle of incidence that causes 90° angle of refraction
5.1P
How do you draw a ray diagram?
-Single straight arrow
-Arrow shows direction
5.2P
Draw a diagram of specular reflection
Only look at top diagram
https://www.ecosia.org/images?q=specular%20reflection#id=1A940C3EAFF1B23F92BB1802A140EEBB5116CBEA
5.2P
Draw a diagram of diffuse reflection
https://www.ecosia.org/images?q=specular%20reflection#id=1A940C3EAFF1B23F92BB1802A140EEBB5116CBEA
5.2P
Explain the differences between specular and diffuse reflection
Specular
-Produce clear reflection (like mirror)
-Because all light rays reflected in same direction
Diffuse
-Will not
-Because light rays scattered
5.3P
What is a luminous object?
Emits own light
5.3P
What is a non-luminous object?
-Doesn’t emit own light
-Reflects light from luminous objects
What is white light composed of?
All colours of visible light
5.3P
What is a filter?
-Material that transmits & reflects only 1 colour of light
-All others absorbed
5.3P
If a blue and red filter are placed in front of each other and white light is shone at them, what will you see?
Nothing
Blue filter transmits blue light only which will then be absorbed by the red filter
5.4P
Describe the properties of a powerful lens
-Thick
-Shorter focal length
5.5P
Draw a ray diagram for a converging lens, for an object at 2F and describe the image
https://www.ecosia.org/images?q=ray%20diagram%20for%20converging%20lens%20for%20object%20outside%202F#id=8C8A4EA77D99DD024B8D6015149572F298FFA4C2
-Real, inverted, same size
5.5P
Draw a ray diagram for a diverging lens, for an object outside 2F and describe the image
https://www.ecosia.org/images?q=ray%20diagram%20for%20diverging%20lens%20for%20object%20outside%202F#id=8B74B2C8E1CCBA23ADDF749D34BD592414F4C5DC
-Virtual, erect, diminished
5.5P
You are drawing a ray diagram of a converging lens and your two rays don’t meet, what do you do? Describe the image
-Trace them backwards using virtual rays
-Find point where they meet and draw image
-Image will be virtual, erect, magnified
5.6P
What effect does a converging lens have on parallel light rays? Therefore, what type of image does it produce?
-FOCUS & meet at point
-Focal point can be focused on screen -> real image
5.6P
What effect does a diverging lens have on parallel light rays? Therefore, what type of image does it produce?
-Spread out from point
-Focal point can’t be focused on screen -> virtual
What is a focal point?
Point where PARALLEL light rays meet/appear to originate from
What is a focal length
d from focal point to centre of lens
What do you call an image that can be projected?
Real
What do you call an image that can not be projected?
Virtual
What do you call an image that is the opposite way up?
Inverted
What do you call an image that is the right way up?
Erect
What do you call an image that is bigger than before?
Magnified
What do you call an image that is smaller than before?
Diminished
5.7
Are all electromagnetic waves transverse or longitudinal?
Transverse
5.7
At what speed do electromagnetic waves travel in a vacuum?
3×10^8 m/s
5.10
State the electromagnetic spectrum in order starting with the lowest frequency
-Raw Meat Is Very Unsanitary eXcept Giraffes
-Radio waves
Microwaves
Infrared
Visible light
Ultraviolet
X-ray
Gamma rays
Describe the relationship between frequency and wavelength
Inversely proportional
5.11
Which electromagnetic wave has the highest frequency? And therefore ___ wavelength
-Gamma rays
-Shortest
5.11
Which electromagnetic wave has the lowest frequency? And therefore ___ wavelength
-Radio waves
-Longest
Which colour of visible light has the Lowest frequency and Longest wavelength?
Red
5.12
How much of the electromagnetic spectrum can our eyes detect?
Visible light only
5.14H
Why can colours of visible light be separated out by refraction?
Diff wavelengths -> travel at diff speeds -> refract diff
5.16PH 5.17PH
Explain what needs to happen for the Earth’s temperature to stay constant, and why it’s increasing?
-Needs to emit same radiation/heat it absorbs
-Emits less heat than it absorbs
5.17PH
What would happen to the Earth’s temperature if it started to emit more heat than it absorbed?
Cool down
5.18PH
Explain the green house effect
-Short wavelength Infrared radiation emitted from sun to Earth
-Absorbed by Earth -> hotter
-Earth emits longer wavelength Infrared radiation
-Some absorbed by water vapour + CO₂
-Emit BACK to Earth -> even hotter
5.18PH
How can we reduce the greenhouse effect?
Remove some CO₂ -> decreases emitted Infrared radiation -> Earth cools
5.19P
State the independent, dependent and control variables in the colour vs emission practical
-I: Colour of paper
-D: Temperature of water
-C: Type of material
Same thickness
Same VOLUME of boiling water
Same initial temp of boiling water
Time interval at which you measure results
5.19P
What is a safety hazard and precaution that must be taken in the colour vs emissions practical
-Hot water
-Be careful
5.20
If the frequency of an electromagnetic wave is high, what does that mean in terms of its dangers?
More dangerous
5.21
What are the dangers of radio waves?
Non-existent
5.21
What are the dangers of microwaves?
Internal heating of body cells
5.21
What is a danger of infrared radiation?
Skin burn
5.21
What are the dangers of visible light?
Damage to eyes
5.21
What are the dangers of ultraviolet radiation?
-Sunburn
-Skin cancer
5.21
What are the dangers of x-rays?
Cause mutations -> cancer
5.21
What is a danger of gamma rays?
Cause mutations -> cancer
5.21
Why does current scientific evidence tell us that mobile phones (which use microwaves) are not a health risk?
Use lower frequency
5.21
Why do microwaves have a metal plate/grid inside the door?
Metal grid reflects microwaves but holes allow visible light through
5.21
How can we reduce the damage from infrared & ultraviolet radiation?
Sun cream
5.22
What are the (2) uses of radio waves?
-Communications
-Transmitting broadcasts
5.22
What are the (2) uses of microwaves?
-Communications
-Heating food
5.22
What are the (5) uses of infrared radiation?
-Cooking
-Thermal imaging
-Security cameras
-Communication
-Optical fibres
5.22
What are the (2) uses of visible light?
-Seeing
-Photography
5.22
What are the (3) uses of UV radiation?
-Disinfect water (kill bacteria)
-Security (fluorescence)
-Low energy light bulbs
5.22
What are the (2) uses of x-rays?
-Medical imaging
-Airport security
5.22
What are the (2) uses of gamma rays?
-Sterilisation (food + surgical equipment)
-Detect/kill cancer
5.22
Why would there be UV lamps at a sewage works?
To disinfect water to make it potable
5.22
Why are water bottles left outside in the sun in poorer countries?
Sun emits UV light, disinfects water -> potable
5.22
What 2 EM waves are used in energy saving light bulbs? How?
-UV & visible
-Gas inside produces UV radiation
-Glass fluorescent coating absorbs UV and emits visible light
5.23H
Describe how radio waves are produced
-Intentionally by humans
-Electrons oscillating in wires/a.c.
-Aerial (metal rod) absorbs radio waves
(-Oscillations in electrical circuits
-Aerial (metal rod) absorbs radio waves
-Cause oscillations in circuit connected to aerial)?
5.24
Explain how radiation is produced
-Atom absorbs E
-e- excited (moves up ENERGY LEVEL*)
-If loses E, jumps down energy level
-Emits EM radiation
*Not electron shell
*Upper energy levels usually empty
5.24
Explain why an element can emit light at lots of different wavelengths
Each change in energy levels produces diff wavelength
Why do black objects appear black?
They absorb all wavelengths
Add specpoint
What is total internal reflection?
<incidence = larger than <critical -> light fully reflects
Compare how radio waves and infrared radiation travel through objects
Radio waves transmitted through
Infrared absorbed
