Unit 3: Light and Telescopes Flashcards
What did Newton believe about light?
- that light is a stream of particles
What did Hooke believe about light?
- light is a process like sound (waves)
What did Newton find about prisms
- newton found that the prism itself does not add the colour to the light but that the colour is an intrinsic property of light
What does a prism split white light into?
What happens when you shine the light through a second prism?
Who found this out?
- 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)
Who predicted and confirmed electromagnetic waves?
- James Clerk Maxwell predicted them in 1860
- 20 years later this was confirmed by Heinrich Hertz
What is wavelength ?
- the distance between two peaks in a wave
What differentiates electromagnetic waves from other types of waves like sound waves and water surface
- electromagnetic waves can propagate through an empty space (vacuum)
What wavelengths are visible to humans
- 400 to 700 nm
What is the speed of light referred to
C
C= 300,000 km/s = 180,000mils
What is one of the fundamental principles of physics
- nothing can move faster than light
- the fitness of the speed of light
If the sun went out, how long would it take for us to know?
8 minutes
Is light particles or waves?
- its both
What is the order of waves starting with the longest
- radio waves
- microwaves
- infrared radiation/ light
- visible/ white light
- ultraviolet radiation/ waves
- x-ray waves
- gamma rays
What is the Doppler Effect?
What is a Red shift?
What is a Blue shift?
- 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
What was Albert Einsteins contribution to light properties
- he showed that light also behaves as particles called photons
- the energy of a photon decreases as it’s wavelength increases
Does a photon of red light carry less or more energy than blue
- less
According to Quantum Mechanics, photons have what properties
- the properties of particles and waves at the same time
- particle-wave dualism
What does the transparency of a material depend on?
Which waves can pass through and which cannot?
- 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
What are the two basic telescopes
- reflecting
- refracting
What are reflecting telescopes
- they use a concave mirror to gather and collect light
- creates focal point
- concave parabolic mirror
- gather and focus
what is the newtonian reflecting telescope
- primary and secondary concave mirrors
- primary mirror focuses light on flat secondary mirror into lens eyepiece
What are the 3 properties and functions of a telescope
- light gathering power
- angular resolution
- magnification
What are the light gathering powers of a telescope and how does diameter affect this
- 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
What is the resolution property of a telescope
How does diameter affect this
- 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
What is magnification
- making objects appear larger
Why is the human eye not very good as light detectors
- they become tired
- eyes cannot take photos, must sketch what u see
Photographic plates
- glass plates covered In silver salts
- light sensitive emulsion
- hard to store
Charge-Coupled Devices (CCDs)
- gather more light efficiently than photographic plates
- they produce images with incredible detail
What are refracting telescopes
- 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
What are the limitations of a refracting telescope
- chromatic aberration- different colours of light have different focal points
- spherical aberration - not all parallel rays converge at a single focal point
- the weight of a lens can cause the lens to sag and distort the image
- air bubbles in glass distort the image
- glass is opaque due to certain wavelength’s of light, meaning they do not go through the mirror
What is the main problem with reflecting telescopes
How do ew fix this
- 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
Where is the largest refracting telescope
- 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
How to make a large parabolic mirror
- 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
Why are many observatories located on mountain tops
- 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)
What is the ultimate solution
- space based telescopes
Why are space-based telescopes better
- the moon has no atmosphere
What is the oldest outer space telescope
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)
Who is james webb
- successor , It has a mirror thats about 14 ft to be able to see way further and will be way further away from earth
What speed do light waves move at in space
- speed of light
What is Nonoptical Astronomy Whats an example What is it used for Where is it located what is the diameter
- 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
What is the very large aray (VLA)
- 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
What is the Spitzer space telescope
what did nonoptical images find
- will examine infrared cosmos
- nonoptical images of the sun reveal detail that other wise cannot be seen
