Topic 11: Exploring the Solar System Flashcards
What is refraction?
The bending of light when it passes from one medium to another, for example from air to water or air to glass.
Draw a basic diagram of Galileo’s refracting telescope
How did Kepler improve Galileo’s refracting telescope design?
He swapped the concave lens that Galileo used at the eyepiece with a convex lens.
This meant that rays of light emerging from the eyepiece are converging. This made for a clearer image.
What is meant by the term ‘field of view’?
is the circle of sky visible through the eyepiece
What is meant by the term light-grasp and how is it calculated?
- The amount of light a telescope can take in.
- The light grasp of a telescope is directly proportional to the square of the diameter of the objective element.
How do you calculate the magnification of a telescope?
magnification = objective focal length ÷ eyepiece focal length
How do you calculate the magnification of a telescope?
magnification = objective focal length
What is dispersion?
the splitting of light in to its component colours, as different colours of light have different wavelengths they refract different amounts.
What is chromatic aberration?
Chromatic aberration occurs when a lens fails to focus the different wavelengths of light at the same point making the image blurry and unclear.
Only a problem with refracting telescopes.
Give 3 advantages of reflecting telescopes.
- larger objective apertures
- mirrors reflect light with almost no loss of intensity, unlike lenses
- don’t suffer from chromatic aberration
- tend to be smaller in size and therefore more practical to use
What is the basic difference between a refracting and reflecting telescope?
- Refracting telescopes use a convex (converging) lens to capture and focus light.
- Reflecting telescopes use a parabolic concave (mirror) to capture and focus light.
Describe how an optical telescope works.
- The objective element collects as much light as possible and focuses the light to a small bright image.
- The image is the magnified by an eyepiece lens so that the astronomical object can be observed in much more detail (higher resolution) and brighter than when looking with the naked eye.
What is meant by a telescope’s size or aperture?
The diameter of the telescopes objective lens or mirror
Give 2 advantages of having a telescope with a larger aperture.
- more light enters the telescope, making the images brighter
- you get ‘sharper’ images, higher resolution images
Why is the human eye a poor tool for astronomical observations?
The human eye has a small aperture so it does not let in very much light so it is bad at seeing dim objects.
Draw a diagram of the objective lens of a refracting telescope.
A curved lens, it focuses light to an image at the focal point. See diagram
Explain the position of the eye piece in a refracting telescope.
The eye piece needs to be after the focal point.
The light rays diverge at the focal point before hitting the eye piece and becoming parallel again before entering the eye
Draw a diagram of a concave mirror, label the focal point and focal length
F is the focal point (ignore the c)
Draw a diagram of a reflecting telescope and explain where the position of the eyepiece needs to be.
The eyepiece is on top of this Newtonian reflecting telescope.
Where the light rays converge.
Which can support a bigger aperture; a refracting or reflecting telescope?
A reflecting telescope because the objective lens is at the back end of the telescope giving it a lower centre of mass. This makes the telescope more stable and able to support a bigger aperture.
Mirrors are also cheaper and easier to manufacture than lenses.
A student has 2 telescopes of the same size and tube length. One telescope is a reflector and the other is a refractor. The student say ‘ the reflector has a longer focal length than the refractor.’ Is the student correct? Explain your answer
Correct because a reflector has more mirrors. The more mirrors you add the greater the focal length.
What benefit does having multiple mirrors in a reflecting telescope have?
More mirrors = greater focal length
greater focal length of the objective = greater magnification
Give 4 disadvantages of refracting telescopes.
- Lenses absorb light making images dimmer
- Lenses do not refract different wavelengths of light to the exact point (chromatic aberration), causing images to be blurry
- Lenses can sag under their own weight, altering their shape and causing distorted images
- It is also difficult to manufacture clear glass lenses that have no blemishes
Explain why bigger is better when it comes to telescopes
- brighter the image
- shorter time needed to collect data from the astronomical object
- better resolution (ability to see fine detail in the image)
What is the approximate diameter of the pupil of the human eye in bright light?
3mm
Which photoreceptors in the human eye respond to bright lights?
cones
What is the name of the naked eye observing technique in which an observer first spends about 30 minutes outside to allow the retina’s rods to desensitise.
Dark adaptation
Which part of the human eye allows light to enter?
pupil
Describe the composition of the Earth’s atmosphere
Thick
78% nitrogen
21% oxygen
1% other gases including CO2, argon, water vapour
What is the mean distance from the Earth to the Sun?
150 million km or 1 astronomical unit (AU)
Why is there life on Earth?
Because it lies in the Goldilock’s Zone of the solar system. The Goldilock’s Zone is a habitable zone just the right distance from a ‘sun’