Light & Optics 1-2 Flashcards
(41 cards)
1
Q
What did Archimedes do?
A
- Archimedes (yes, the guy
with the screw) created an
invention to burn boats - Used a series of mirrors
and lenses - Would focus light on boats
in the Syracuse Harbour
2
Q
What did Euclid do?
A
- Another Greek mathematician
- Shining a light on a flat mirror
- Suggested light travels in
straight lines - Discovery:
–The angle of the incoming
beam is equal to the angle of
the reflected beam
3
Q
What is ptolemy?
A
- Described the bend of light going
from air to glass. - A principle we now know as
refraction (more on that later
in the unit)
4
Q
What was the correlations between Newton and light?
A
- Very interested in rainbows and
light - Shone white light through a prism
–It separated into the colours of
the rainbow - Passed the rainbow through a
second prism
–Colours combined and the light
was white
5
Q
What is the speed of light and how was it determined?
A
- Early scientists knew light travelled, just not how fast
- Mirrors were placed on two different mountains and
sensitive timing devices were used - Beam of light was sent from one mirror to the
other - By dividing distance by time speed of light was
determined as 299 798 km/s.
6
Q
What are the (4) basic properties of light?
A
- Light travels in straight lines.
- Light can be reflected.
- Light can bend.
- Light is a form of energy.
7
Q
What is an optical device?
A
- Any device that
uses light - It could be a
mirror (simple)
or the Hubble
telescope
(complex)
8
Q
When were microscopes made?
A
- First microscope is believed
to have been built in 1595
Hans and Zacharias Jansen of
the Netherlands - Very simple design, but led to
great discoveries
9
Q
Who was Antonie Van Leeuwenhoek?
A
- Dutch amateur scientist
- Experimented with a simple
microscope - Looked at things like pond water,
blood and his own tooth plaque - He saw small moving organisms
which he called “little animalcules”, a
shock to the scientific community!
10
Q
What is microbiology?
A
The study of micro organisms
11
Q
How do microscopes work?
A
- Combine the power of at least
two lenses so you can see great
detail - Two lenses are: Eyepiece and
objective - Light shines through the
specimen and a large image is
produced by looking through the
eyepiece
12
Q
When were telescopes made?
A
- Early astronomers used a
single lens to get a better
look at the stars - The telescope
revolutionized astronomy - First telescope: 17th century
Netherlands
13
Q
Who was Galileo Galilei?
A
- Heard about the telescope and
made his own in a day- it wasn’t
great, but it did the job - Began developing better higher
power telescopes - Amazing astronomical discoveries
- Telescopes have two characteristics:
– Magnify
– Collect light
14
Q
What is a refracting telescope?
A
- Have two lenses, one at each
end of a long tube - Larger objective lens collects
light, focuses light on the eye
piece - In turn you see the image larger
than with an unaided eye
15
Q
What is a reflecting telescope?
A
- Use a large circular mirror
- Mirror is curved so it collects
light extremely well - Another mirror directs the
light to the eyepiece
16
Q
What are binoculars?
A
- Just two short
refracting telescopes! - Not as powerful as
telescopes - More convenient
because they’re smaller
17
Q
What are ray diagrams?
A
- Show how light travels
- Light travelling from a source is shown in
straight lines - Each ray ends with an arrows, indicating
direction of travel - Light rays travel from a source in every
direction - Millions of rays of light leave a source, we
only draw a few to get the general idea
18
Q
What is the correlation between ray diagrams and intensity?
A
- Ray diagrams can help explain
why brightness (intensity)
changes with distance - In the diagram we can see the
same amount of rays leaving the
light source. - Fewer hit your eyes when it is
farther away
19
Q
How do ray diagrams and shadows relate?
A
- Ray diagrams can also
explain shadows - If light hits an object it can’t
go through it - An object between light and
our eyes is perceived as a
shadow
20
Q
How does light react with materials?
A
- When light hits an object it behaves in different ways
depending on what the object is made of
21
Q
What is transparent?
A
- Examples: glass, clear plastic
- Can transmit light
- Light travels straight through
them - This is why you can see clear
through a window
22
Q
What is translucent?
A
- Example: frosted glass
- Allow some, but not all light
through - You can’t see things on the other
side in detail
23
Q
What is opaque?
A
- Examples: wood, metal, brick
- Do not allow light to pass
through - Absorb or reflect the light
that hits them - Shadow is created behind
opaque objects
24
Q
What are non-luminous objects?
A
- They DON’T produce light
- For light to get to your eyes
it must reflect off the object - Light comes from a light
source
25
What are luminous objects?
* An object that produces light
* Provide the light to see non-
luminous objects
* Examples: sun, a lamp
26
What is regular reflection?
* When light rays hit a smooth surface
* Incoming rays travel parallel to one another
* Hit a smooth surface and all bounce off in the same direction
* The rays stay parallel to each other
* Shinier and smoother the surface the better the reflection
27
What is diffuse reflection?
* When light rays strike a rough or uneven surface
* Due to the rough surface each light ray is reflected in a
different direction
* Reflected rays do not remain parallel
28
What are incident rays?
Incoming rays of light.
29
What are plane mirrors?
* Flat mirrors
* Provide the clearest reflections
* We can use them to investigate how reflected light behaves
30
What is the law of reflection?
* When a ray of light hits a plane mirror it bounces off the surface
at the same angle
* Normal: A line perpendicular to the mirror at the point of
reflection
* Angle of incidence: angle between the incident ray and the
normal
* Angle of reflection: angle between the reflected ray and the
normal
* Angle of incidence = angle of reflection
31
What are funhouse mirrors?
* Strange imaged produced by flat,
inward and outward curved
sections of the mirror.
* Mirrors like this have no real
practical use
* Single curves in mirrors, however,
are useful
32
What are concave mirrors?
* Surface curves inward like a bowl
* Obey the law of reflection
* Light rays strike on a different point on the curve
* All rays head to a common point, the focal point
* Good at collecting light and bringing it to a single point
* Ideal for reflecting telescopes
33
What are the images in concave mirrors like?
* Image formed will depend on how far the object is from
the focal point of the mirror
* Far away= upside down image
* Closer to the focal point = larger the image (still upside
down)
* Object between the focal point = enlarged and upright
34
What are convex mirrors?
* Mirror with a surface curved outward
* Spreads out light rays
* Appears as if the image originates from a smaller point
behind the mirror
* Example: often used on cars
–Often have the warning “Objects in the mirror are
closer than they appear”
35
What is refraction?
* When light travels at an angle from one substance to
another it bends
* Due to changes in the speed of light
* In a vacuum light travels 300 000km/s
* It’s impossible to move at top speed with particles in the
way
36
How does refraction work?
* When light strikes a
different density it bends
* Part of the beam of light will
hit the new medium first and
go slower or faster
* The rest will keep going at
the same speed
–Causes a bend
37
How is refraction different in different media?
* Denser the new medium
is the more it refracts
* Example: a diamond is
much denser than water
and refracts light more
than water does
38
What is a lens?
* A piece of curved glass or other
transparent material
* Smooth and regularly shaped
* When light hits it the light will
refract in a predictable way
39
What are concave lenses?
* Thinner at the centre than the ends
* As parallel rays pass through they are
refracted away from the centre of the lens
* Rays diverge and will never meet on the
other side of the lens
40
What are convex lenses?
* Thicker in the middle than the ends
* As parallel beams of light move through the convex lens
they are refracted towards the centre
* Light rays cross at the focal point of the lens
* Can act as a light collector
* Used in refracting telescopes
* Light rays meet at a point, so we could project them on a
screen
* Problem: image is often upside down
41
How does image formation work with convex lenses?
* Depends on how far the object is from the lens
* If the object is past the focal point it will appear upside
down and either smaller or bigger depending on how far
* If the object is between the focal point and the lens it will
appear bigger and upright
