Science Test Ph Wk. 2 2018 (9e)

Question 1

Define: Wavelength

Answer 1

The distance between the crests of a wave

Question 2

Define: Frequency

Answer 2

The number of oscillations of a wave in a given amount of time, usually seconds.

Question 3

Define: Amplitude

Answer 3

The size of the oscillation, the distance between the equilibrium (center of the wave)

Question 4

Define: Pitch

Answer 4

The pitch of a note is how “high” the note is, and this depends on the frequency of the wave.

Question 5

Define: Loudness

Answer 5

The loudness depends on the amplitude of the wave. The larger amplitude, the louder the wave.

Question 6

Define: Vacuum

Answer 6

A space where there is no matter.

Question 7

Define: Echo

Answer 7

A sound caused by the reflection of sound waves. This happens when some of the sound wave bounces of a surface.

Question 8

Define: Infrasound

Answer 8

Sound waves with lower frequency than detectible by the human ear. Anything < 20 Hz. Can be used to transmit signals.

Question 9

Define: Ultrasound

Answer 9

Sound waves with a frequency > 20 kHz. These can be used as a replacement for X-ray, since it is way less dangerous, however the images it produces are a lot less sharp. How this is done is an ultrasound wave is sent into an object, and the sound wave passes through the entire object, but each time it hits something, some of it is bounced, off, so we get multiple reflections, and with that we can find abnormalities, or produce images.

Question 10

Define: Bioluminescence

Answer 10

The biochemical emission of light by living organisms such as glow-worms and deep-sea fish.

Question 11

Define: Chemiluminescence

Answer 11

The emission of light during a chemical reaction which does not produce significant quantities of heat.

Question 12

Define: Emit

Answer 12

To give off light.

Question 13

Define: Absorb

Answer 13

To take in light and convert it to heat

Question 14

Define: Reflect

Answer 14

When light bounces off a surface

Question 15

Define: Scatter

Answer 15

When light hits an object, and is sent in all different directions.

Question 16

Define: Transmit

Answer 16

To allow light to pass through something.

Question 17

Define: Refract

Answer 17

To bend light.

Question 18

Define: Opaque

Answer 18

An object which light cannot pass through

Question 19

Define: Translucent

Answer 19

An object which allows some light to pass through it.

Question 20

Define: Transparent

Answer 20

An object which allows all light to pass through it.

Question 21

Define: Lenses

Answer 21

A transparent material which refracts lights to the point where they either converge to a point or diverge from a point.

Question 22

Define: Concave

Answer 22

A concave lens causes light to diverge, while a concave mirror causes light to reflect and converge to a focal point.

Question 23

Define: Convex

Answer 23

A convex lens causes light to converge to a focal point, while a convex mirror causes light to reflect and diverge outwards from the source of light.

Question 24

Define: Converge

Answer 24

When light rays are focused to a single point, making the distance between them smaller as you go along.

Question 25

Define: Diverge

Answer 25

When light rays are focused away from a single point, making the distance between any point of a light ray and a the corresponding distance from the focal point increase as the distance from the focal point increases.

Question 26

Define: Mirages

Answer 26

When light travels in a non-uniform medium, it may gradually speed up or slow down, which will cause it to change direction. For example, if the air on the ground is really hot, but the higher up you go, the air becomes colder, you have a non-uniform medium. The hotter air is less dense, and therefore, when light travels from a higher point down to a lower point, the change in density will cause the light to change speed, and alas change direction. This will cause the light to bend upwards, and cause the viewer to see things above the viewers eyes. Crazy right?

Question 27

Define: Fiber Optics Spectrum

Answer 27

To be continued.,

Question 28

Define: Gamma ray (bands)

Answer 28

Gamma rays are a form o electromagnetic radiation. It is a form of light which extremely an extremely small wavelength, in fact it is the most energetic wave in the electromagnetic spectrum. Gamma rays can be used to treat cancer. And gamma ray bursts are a thing we really don’t want to come near us because then we’re fucked.

Question 29

Define: X rays

Answer 29

Light waves with very small wave-lengths, the second most energetic wave on the electromagnetic spectrum,. It is able to pass through many opaque materials, and is used to produce images of the insides of for example the human body, in order to e.g. treat cancer.

Question 30

Define: Ultra-violet rays

Answer 30

Light waves which are invisible to the eye because they have, a wavelength which is shorter than what is visible to the human eye. Ultraviolet rays are transmitted by the sun, and can cause different types of skin cancer :(

Question 31

Define: Infra-red

Answer 31

Light waves which have wavelengths longer than what is visible to the human eye. Uses of infrared light include being able to amplify light in low light situations (night vision) or thermography, being able to extract heat data from objects.

Question 32

Define: radio waves

Answer 32

Radio waves are waves which have a longer wavelength than infrared waves. Uses of radio waves include literal microwaves (duh), Tv, and radio and stuff like that.

Question 33

Define: Filter

Answer 33

Filter are materials that only allow certain wavelengths to pass through them. RED filters only allow RED wavelengths to pass through them.

Question 34

What are the different types of waves?

Answer 34

Longitudinal waves:
* Longitudinal waves are really just energy which causes matter to move in chain reactions. They have crests and throughs where the particles are compressed and rarefracted (expanded). (Sound is this type of wave)
Transverse waves:
* Transverse waves are waves which move up and down, or sideways. The crests are the highest points of the waves, and the throughs are the lowest points of the waves.

Question 35

How is sound caused?

Answer 35

Sound is caused by vibrations which creates distortions in a medium creating longitudinal waves. This is why sound needs a medium to travel through.

Question 36

What is the speed of sound?

Answer 36

In air: 320-350 m/s
In water: 1400 m/s
In Lead: 2000 m/s
In Glass 5600 m/s
Steel: 6000 m/s

Question 37

Define: wavelength, frequency, amplitude, and how they are measured.

Answer 37

Wavelength: The distance between two adjacent crests or throughs in a wave. In longitudinal waves this is the difference between two adjacent rarefactions or compressions.

Frequency: The number of oscillations in a wave per second. 1 oscillation = back and fourth one time.

Amplitude: In transverse waves this is the difference between crests and the equilibrium of the wave, and in longitudinal waves this is the distance between coils in compressions.

Question 38

How is loudness measured?

Answer 38

Loudness is the amplitude of a longitudinal wave, which is measured by measuring the difference between coils in compressions.

Question 39

What is the speed of light?

Answer 39

300 000 000 m / s or 3 * 10^8`t

Question 40

How does light travel?

Answer 40

Light travels in straight lines.

Question 41

What is the order of the rainbow, and why are they in that particular order?

Answer 41

R ed
O range
Y yellow
G green
B blue
I indigo
V violet

They are in this order becuase the color of light depends on its wavelenght, and in reality color is not real, it is simply something evolution caused us see to percieve the world around us, where red light which has the lowest wave lenght of the visible spectrum was seen as red, and all the way up to violet, which has the highest wavelength in the visible spectrum.

Question 42

How do we use echoes for locating objects?

Answer 42

We send an ultrasound to where we think the object is, and when we recieve an echo we know that the ultrasound has bounced off of that object, and if we use the formula d = vt, and we know the time it took for the echo to travel to and from the object, we can simply calculate that d = v(t/2), and with that we can calculate the distance to the object.

Question 43

How is frequency and wavelength related?

Answer 43

Wavespeed = Frequency * Wavelength

Therefore,

Frequency = Wavespeed/Wavelength

And

Wavelength = Wavespeed/Frequency

Question 44

What is the law of reflection?

Answer 44

Angle of incident-ray -> normal = Angle of reflected ray -> normal.

Question 45

What is a normal?

Answer 45

A normal is the direction a surface is pointing in. This can be used to calculate how light will reflect of a surface, since the difference between the incident ray and the normal and the difference between the reflected ray and the normal are always the same.

Question 46

What is a concave mirror and how does it work?

Answer 46

A concave mirror bends inwards, converging all light to a single point, called the focal point.

Question 47

What is a convex mirror and how does it work?

Answer 47

A convex mirror bends outwards, diverging light outwards,.

Question 48

What image should you expect from a convex/concave mirror?

Answer 48

Convex: Convex mirrors widens the image, and generally create wide images because of the fact that the light is spread out.

Concave: With concave mirrors it depends. If you are observing beyond the focal point you will see an upside down image, since the light has been inverted, but if you are at the focal point, you will see everything like regular, although the mirror creates a narrow image, since the light is focused to a single point.

Question 49

What happens to light as it travels from one substance to another, and why?

Answer 49

Light always travels at light speed, however when it hits an atom, it is absorbed, and re-emitted in the same direction, which takes a small amount of time, which means that the time it takes for light to pass through that object increases, decreasing the speed. This causes light to bend, or refract. When travling into a denser material, light will bend towards the normal of the material, and vice versa. If light hits another medium straight on, the light is not refracted.

Question 50

What is the refractive index, how is it calculated and what does it mean.

Answer 50

The refractive index is how much something slows down light compared to light in a complete vacuum. Since light travels fastest in a complete vacuum, all refractive indexes are almost always > 1.
The refractive index is calculated with the following formula:
n = c/v
Where n = refractive index, c = speed of light in vacuum, and v = speed of light in medium.
Water has a refractive index of 1.333, which means that light travels 1.333 times slower in water compared to a vacuum. This also affects how much light is bent. When passing through mediums.

Question 51

Why does a rainbow appear?

Answer 51

Because water droplets acts as prisms and scatter the light, causing it to split into all of its components, creating the rainbow.

Question 52

Why do objects display different colors in white light?

Answer 52

Because different materials absorb different wavelengths, so red materials absorb all light but red, and therefore only red light bounces off of that object, making it appear red.

Question 53

What are the primary colors of light?

Answer 53

RGB

Question 54

Why do mirror images become magnified/diminished/upright/inverted

Answer 54

Magnified: An image is magnified if a large amount of light is focused into a small area, this only happens with concave mirrors where the observing point is not beyond the focal point, since the light is converged to a single point.
Diminished: An image is diminished if a small amount of light is scattered and displayed onto a large area, this happens with convex mirrors since they diverge, causing the light to scatter.
Upright: Images become upright either if they simply are not inverted, as with the case with convex or upright normal mirrors, or when the observation point is at the focal point of a concave mirror, where the light has not yet inverted.
Inverted: Images invert when they hit a concave mirror, because their direction is focued on a focal point, and beyond that the image is inverted.

Question 55

How does refraction, why do swimming pools look shallower than they really are, and why are fish hard to catch just by looking through them through water?

Answer 55

Swimming pools look shallow, because the light is bent in a way that makes creates the illusion that the light is originating from a different point than it actually is. The same is the case with fish, since light bends when it hits objects that are less dense, objects appear in different locations than they actually are in. This is due to that our eyes do not take into account refraction that occurs when light enters another substance.

Question 56

What is meant by critical angles and the size of critical angles of water and glass.

Answer 56

The critical angle of a substance, is the angle at which if light enters the object at said angle, instead of refracting light, it will become totally internally reflective, and reflect light. For this to happen, there are two main conditions that need to be true. First of all, the light must be approaching said substance from a more dense medium. Also, the angle of incidence for the light ray has to be greater than the critical angle. When light travels from air to water, the critical angle is 48.6 degrees. However when light goes from crown glass into water, this angle becomes 60.1 degrees. What this shows us, is that the density difference between the two objects matter. The critical angle for air to glass, is around 42 degrees. To summarize, the critical angle is essentially the angle which light must approach an object for the angle of refraction to become 90 degrees.

Question 57

What is meant by total internal reflection, and explain how it works.

Answer 57

Total internal reflection, is a phenomena that occurs when light travels from a dense medium to a less dense medium, and it does so at a specific angle which is greater than the critical angle between those two substances. When this happens, the angle of refraction becomes 90 degrees, therefore instead of refracting the light, it completely reflects it.

Question 58

The uses of total internal reflection, especially optical fibers.

Answer 58

There are many uses of total internal reflection. It is used for instruments such as telescopes, microscopes, binoculars, spectroscopes, periscopes etc. Total internal reflection is the phenomena that gives diamonds its specific shine. Total internal reflection is also used in optic fibers. This works in the way that light travels in a glass tube, where it keeps hitting the glass at an angle which is greater than the critical angle, causing it to be reflected. Since the light is keeps being reflected forward, signals (of light) can travel through fibers this way, at almost light speed. The way to send signals is to produce short rays of light in specific patterns that the computers can then interpret, and possible send along more signals.

Question 59

Where the spectrum of visible light fits into the whole electromagnetic spectrum, and what other types of electromagnetic waves there are and their uses.

Answer 59

Going from lowest to highest.

• Radio
  
  • Wavelenth of 10^2
  • Frequency of 10^4
  • Uses: Radio, TV, navigation, air-traffic control, cellular telephony and remote controls.
• Micro
  
  • Wavelength of 10^-2
  • Frequency of 10^8
  • Uses: Microwave (causes water and fat molecules to vibrate, which makes the food hot), mobile phones, wifi.
• Infrared
  
  • Wavelength of 10^-5
  • Frequency of 10^12
  • Uses: All objects give of infrared depending on their heat, so we can use infrared cameras to see how hot objects are, or to detect living organisms, since they tend to give away a particular amount of heat.
• Visible light
  
  • Wavelength of 0.5 * 10^-8
  • Frequency of 10^15
  • It is the light that the human eye can interpret.
• Ultraviolet
  
  • Wavelength of 10^-8
  • Frequency of 10^16
  • Given off by the sun, can cause skin cancer, due to the fact that the wavelength is so small, and there is so much energy that they can damage the DNA of cells, and if those cells do not repair correctly then you sir, are fucked.
  • Uses: Sunburns, Vitamin D, drying clothes, sterilize things (UVC)
• X-ray
  
  • Wavelength of 10^-10
  • Frequency of 10^18
  • Uses: Produce sharp images of the inside of humans, scan bags at airports,
• Gamma
  
  • Wavelength of 10^-12
  • Frequency of 10^20
  • Can cause cancer, shatter atoms, can be used to preserve food, or in medical science, if you use it in veeery small amounts. Used to sterilize surgical instruments, kill harmful bacteria in food. Can kill cancer but also create cancer.

Question 60

How have electromagnetic waves impacted society.

Answer 60

• Skin cancer n stuff like that.
• Technology, X-ray scans, cancer treatment, Microwaves, cellular communication, wifi, Sterilization of medical instruments.

Question 61

How are optical fibers important in your life, how are they important in society and on a global scale?

Answer 61

As computers are constantly advancing, so are the needs to be able to communicate and send information between computers quickly. Until optical fibers, it didn’t matter how fast your computers was, you were always limited by the physical speed at which electricity traveled through copper, which is something that you can’t change. This applied especially to cases where the distance between you and the computer you wish to send messages to increases, which also increases the time it takes to send messages, and in certain situations, where a lot of messages are being transmitted every second, this can cause problems. With fiber optics, where now the signals travel at close to light speed, the only limitation is how quick we can interpret these signals. This makes for example realtime multiplayer games a lot easier to create, and you can play with computers that are further away from you. This makes the focus not on sending messages faster, but interpreting them faster, which is something we know we can improve.