🔭W5 L1 - The nature of light - detection with telescopes Flashcards
Learn how telescopes detect electromagnetic radiation
What velocity is needed to orbit planet Earth?
7,300 metres per second
What is the escape velocity for Earth?
11.2 km per second
What is the diameter limit of a lens for a refractor telescope?
1 metre
What’s the largest you can build a reflecting mirror?
8 metres
How accurate do mirrors need to be?
Nanometre level ie 10⁻⁹ metres (10 nanometres)
What’s the diameter of the James Webb Space Telescope primary mirror?
6 metres
What’s the diameter of the ELT primary mirror?
39 metres
What’s the diameter of the pupil of the human eye (on average at night)?
5 millimetres
What’s the formula for area of a circle?
Pi r squared
A = 𝝅.r²
What’s the collecting area ratio of the ELT mirror to the human pupil?
60 million
How much fainter objects can ELT see compared with the human eye?
36 million times fainter
What’s the speed of light in a vacuum?
3 x 10⁸ m/s
What is the colour of light (for a human) determined by?
It’s frequency/wavelength
What is the energy of a photon related to?
It’s frequency/wavelength
State 5 properties of light
1) vacuum speed is 3.10^8m/s 2) colour p wavelength/f 3) E det by wavelength/f 4) wave particle duality 5) bends enter/exit materials (VW3b)
What’s a mnemonic for the EM spectrum?
Ronald McDonald Invented Very Useful X-ray Goggles
What wavelength range does the human eye perceive?
380-750nM
Shorter wavelengths are perceived by humans as:
Bluer
Longer wavelengths are perceived by humans as:
Redder
The wavelength of gamma rays and x-rays is:
Short
The wavelength of infrared, microwave, radio is:
Long
Which 3 wave types are detected in high energy processes?
Gamma rays, x-rays, ultraviolet
Name 3 things that observations focused on gamma-rays, x-rays, and UV can detect
Supernovae, pulsars, black holes
Name 2 things in space that can be detected using infra-red and microwave wavelengths?
1) dust 2) warm objects
Name 2 things radio waves are useful for studying in space
1) Hydrogen, 2) magnetic fields of galaxies
What does UV, XR and gamma ray astronomy show is at the centre of the Crab Nebula?
A pulsar
Which retinal cells detect intensity in the eye?
Rods
Which retinal cells detect colour?
Cones
Which cells are more numerous in the human eye?
Rods
What are 6 advantages of photographic plates vs the human eye?
Finder.SCOPE
1) Filterable, 2) Sensitivity higher, 3) Colour, 4) Objective, 5) Permanent, 6) Exposure longer
Which 2 wavebands does the atmosphere most allow through?
1) visible, 2) radio
