Unit 3: Light and Telescopes

Question 1

What did Newton believe about light?

Answer 1

• that light is a stream of particles

Question 2

What did Hooke believe about light?

Answer 2

• light is a process like sound (waves)

Question 3

What did Newton find about prisms

Answer 3

• newton found that the prism itself does not add the colour to the light but that the colour is an intrinsic property of light

Question 4

What does a prism split white light into?
What happens when you shine the light through a second prism?
Who found this out?

Answer 4

• a prism breaks light into its spectrum (ROYGBV)
• though using screens and a second prisms newton found that depending on the screen using, only certain color will pass, but the second prism only changes the direction
• different colours correspond to different types of light particles (newton)

Question 5

Who predicted and confirmed electromagnetic waves?

Answer 5

• James Clerk Maxwell predicted them in 1860

- 20 years later this was confirmed by Heinrich Hertz

Question 6

What is wavelength ?

Answer 6

• the distance between two peaks in a wave

Question 7

What differentiates electromagnetic waves from other types of waves like sound waves and water surface

Answer 7

• electromagnetic waves can propagate through an empty space (vacuum)

Question 8

What wavelengths are visible to humans

Answer 8

• 400 to 700 nm

Question 9

What is the speed of light referred to

Answer 9

C

C= 300,000 km/s = 180,000mils

Question 10

What is one of the fundamental principles of physics

Answer 10

• nothing can move faster than light

- the fitness of the speed of light

Question 11

If the sun went out, how long would it take for us to know?

Answer 11

8 minutes

Question 12

Is light particles or waves?

Answer 12

• its both

Question 13

What is the order of waves starting with the longest

Answer 13

• radio waves
• microwaves
• infrared radiation/ light
• visible/ white light
• ultraviolet radiation/ waves
• x-ray waves
• gamma rays

Question 14

What is the Doppler Effect?
What is a Red shift?
What is a Blue shift?

Answer 14

• Evidence of a wave behaviour of light
• the change in wavelength of light and sound waves due to the relative motion between the source and the observer along the line of sight
• for example, when a cop drives by the sound is the loudest when it is closest or most in line with you
• red shift= moving away from observer, longer, behind
• blue= moving toward observer, shorter, infront

Question 15

What was Albert Einsteins contribution to light properties

Answer 15

• he showed that light also behaves as particles called photons
• the energy of a photon decreases as it’s wavelength increases

Question 16

Does a photon of red light carry less or more energy than blue

Answer 16

• less

Question 17

According to Quantum Mechanics, photons have what properties

Answer 17

• the properties of particles and waves at the same time

- particle-wave dualism

Question 18

What does the transparency of a material depend on?

Which waves can pass through and which cannot?

Answer 18

• wavelength of light “windows” in the earth’s atmosphere
• radio, visible waves can travel through
• x rays, gamma, cannot (easier to observe )
• UV and infrared are partial

Question 19

What are the two basic telescopes

Answer 19

• reflecting

- refracting

Question 20

What are reflecting telescopes

Answer 20

• they use a concave mirror to gather and collect light
• creates focal point
• concave parabolic mirror
• gather and focus

Question 21

what is the newtonian reflecting telescope

Answer 21

• primary and secondary concave mirrors

- primary mirror focuses light on flat secondary mirror into lens eyepiece

Question 22

What are the 3 properties and functions of a telescope

Answer 22

• light gathering power
• angular resolution
• magnification

Question 23

What are the light gathering powers of a telescope and how does diameter affect this

Answer 23

• telescopes brighten objects by collecting light. the ability of a telescope to collect light is called its light gathering power
• smaller diameter means less light gather power, blurred or dimmed image
• larger diameter means more light gathering power, brighter, sharper image

Question 24

What is the resolution property of a telescope

How does diameter affect this

Answer 24

• the clarity of the image and the amount of detail revealed is called angular resolution
• smaller diameter telescopes have less resolution, meaning less details are seen
• larger diameter telescopes have more details and more resolution

Question 25

What is magnification

Answer 25

- making objects appear larger

Question 26

Why is the human eye not very good as light detectors

Answer 26

- they become tired | - eyes cannot take photos, must sketch what u see

Question 27

Photographic plates

Answer 27

- glass plates covered In silver salts - light sensitive emulsion - hard to store

Question 28

Charge-Coupled Devices (CCDs)

Answer 28

- gather more light efficiently than photographic plates | - they produce images with incredible detail

Question 29

What are refracting telescopes

Answer 29

- a convex lens converges parallel light rays at a focal point, just like reflecting telescopes - they use an objective lens to gather light and an eyepiece through which the image is viewed. - this is the telescope that produces an image that is upside down but there is no up and down in space so it doesn't matter

Question 30

What are the limitations of a refracting telescope

Answer 30

1. chromatic aberration- different colours of light have different focal points 2. spherical aberration - not all parallel rays converge at a single focal point 3. the weight of a lens can cause the lens to sag and distort the image 4. air bubbles in glass distort the image 5. glass is opaque due to certain wavelength's of light, meaning they do not go through the mirror

Question 31

What is the main problem with reflecting telescopes | How do ew fix this

Answer 31

- spherical aberration not all parallel rays converge at a single focal point -problem - spherical mirror - how to fix this? use a parabolic mirror so there is one focal point for all light rays

Question 32

Where is the largest refracting telescope

Answer 32

- yerkes observatory near chicago | - the objective lens is 102 cm or 40 inch in diameter and the telescope tube is 19 1/3 m or 63 1/2 ft long

Question 33

How to make a large parabolic mirror

Answer 33

- 40,000 pounds of glass are loaded into a rotated furnace and heated to 1200 degree Celsius - after melting, spinning, and cooling, the surface is ready to be coated with a highly reflective material

Question 34

Why are many observatories located on mountain tops

Answer 34

- starlight appears less distorted in the thin atmosphere on mountain tops - at high altitudes there is less atmosphere to absorb infrared energy - mountain tops also have unobstructed views of the horizon in all directions - light from cities scatter in our atmosphere reducing the visibility of celestrial objects (light pollution)

Question 35

What is the ultimate solution

Answer 35

- space based telescopes

Question 36

Why are space-based telescopes better

Answer 36

- the moon has no atmosphere

Question 37

What is the oldest outer space telescope

Answer 37

the hubble space telescope - launched in 1990 - its primary mirror is about 2 meters in diameter - it has solar panel's to power and is expected to work for 30 years (till 2020)

Question 38

Who is james webb

Answer 38

- successor , It has a mirror thats about 14 ft to be able to see way further and will be way further away from earth

Question 39

What speed do light waves move at in space

Answer 39

- speed of light

Question 40

``` What is Nonoptical Astronomy Whats an example What is it used for Where is it located what is the diameter ```

Answer 40

- the Arecibo radio telescope - the huge dish is 305 m in diameter mounted in a crater of an extinct volcano - the surface is made of almost 40,000 aluminum panels - now we only use it to search for extraterrestrial life

Question 41

What is the very large aray (VLA)

Answer 41

- in central new Mexico combines the signals from 27 radio telescopes - the radio telescope in green bank west virginia - radio waves: we use false-colour images when displaying data from non-visible light

Question 42

What is the Spitzer space telescope | what did nonoptical images find

Answer 42

- will examine infrared cosmos | - nonoptical images of the sun reveal detail that other wise cannot be seen