Chapter 6 Telescopes Flashcards
What are the two types of telescopes?
Refracting telescopes and reflecting telescopes
How do refracting telescopes work?
Refracting telescopes bend (refract) incoming light through a tube to a focal point.
What are the two types of lenses in a refracting telescope?
An objective lens at the front through which light comes through first and an eye piece which magnifies the image.
How does a reflecting telescope work?
a reflecting telescope uses mirrors to reflect light to a focal point.
What are the mirrors in a reflecting telescope?
A primary mirror is a big curved mirror at the back that starts to focus the light, and the secondary mirror is a smaller mirror at the front that redirects the light towards your eye. There is also an eye piece lens.
Which type of telescope is better?
each one has advantages and disadvantages depending on what you want to look at.
What do most modern observatories use?
Most modern observatories use reflectors because the telescopes are so huge.
What is aperture?
Aperture is the diameter of the opening on the front. The bigger the aperture the more light enters the telescope
Why do telescopes need large apertures?
Telescopes need large apertures because the starts only give off dim light, so the aperture needs to be large to let in as much light as possible.
What is focal length?
Focal length is the length from the aperture to the focal point in the telescope.
What happens as the focal length gets longer?
The longer the focal length the smaller the patch of sky you can see, but the greater the magnification.
Why do reflecting telescopes have an advantage when it comes to focal length?
Refractors bend the light down the tube, the tube has to be at least as long as the focal length, but in reflecting telescopes the mirrors reflect the light so the tube can be shorter.
What does a telescope do?
A telescope collects light from distant objects using a lens or a concave mirror
How does gathering more light help to see distant objects?
Distant objects appear brighter, so then they can be magnified bigger to look closely at them
How are simple microscopes and simple refracting telescopes similar?
both have an objective lens and an eye piece lens which bend the light to focus it
What does the objective lens do?
the objective lens collects the light and focusses it into an image
What does the eye piece lens do?
the image is refracted to the eye piece which then enlarges/magnifies it.
What is the focal point in a microscope or telescope?
the focal point is where the light converges
What is a problem with refracting telescopes?
to get a detailed image, the objective lens must be large, which makes it heavy and easy to bend the tube
What has the weight problem of refracting telescopes meant to inventors?
they had to invent the reflecting telescope.
How is a reflecting telescope different?
concave mirror, plane mirror, and a convex lens to collect and focus light
Explain the path of light in a reflecting telescope?
light enters, bounces up off a concave mirror, hits an angled plane mirror just before the focal point, then bounces towards the eye piece. The convex lens in the eye piece magnifies the image
What does the Keck telescope in Hawaii do?
The Keck has several mirrors so the image is larger.
What is the Hubble space telescope?
the Hubble is a telescope that orbits the earth.
Why would it be better to look at space from space?
The earth’s environment clouds images, so the image is clear from space
What kind of telescope is the Hubble?
the Hubble is a reflecting telescope.
How big are the Hubble’s mirrors?
2.4 m across.
Does the Hubble only detect light?
No, the Hubble detects electromagnetic radiation as well as light.
