Ch 04: Homework

Drag and drop each of the labels to the appropriate part of the telescope.

left: B. Objective lens right: A. Focal plane bottom: C. Focal length

The bright, colorful "stripes" of a rainbow such as the one shown here follow a particular order. Rank each color of the rainbow by how much energy is carried by its electromagnetic waves, from highest to lowest.

1) Blue 2) Yellow 3) Orange 4) Red

Refracting telescopes use lenses to focus light onto the focal plane. The diagram below shows the path of the light rays for two stars through two different telescopes. Each telescope has a lens with a different shape. The different shapes change the way the light is refracted through the telescope, resulting in images that appear different through each telescope. Based on the light rays for stars 1 (blue) and 2 (red), label each telescope with how the image of the stars will appear, as compared to the other telescope.

A. Inverted image, stars closer together C. Inverted image, stars farther apart

Besides adding adaptive optics to a telescope, what else can be done to reduce the effects of seeing?

A. Put the telescope at a higher altitude (the height above sea level).

Sort the following properties of telescopes with their corresponding definitions.

Aperture: Diameter Resolution: Ability to distinguish objects that appear close together in the sky. Focal Length: Distance from lens to focal plane Chromatic: Rainbow-making effects Diffraction: Smearing effect due to sharp edge Interferometer: Several telescopes connected to act as one

The largest astronomical refractor has an aperture of 1 meter. Select all true statements below about why it would be impractical to build an even larger refractor with, say, twice the aperture.

B. The degree of chromatic aberration increases as the focal length gets longer, and this would reduce image quality. C. The tube would have to be so long that housing and moving it would be extremely difficult, especially because it would be frontloaded with weight. D. A lens with a 2 m diameter would be very heavy and would deform under its own weight within a few years.

Based on the time frames given in the above figure, which of the following are implications of the finite speed of light?

B.When we gaze at the Andromeda Galaxy, we are looking back in time to the way it used to appear millions of years ago. D.If the light of the Sun were suddenly extinguished, we wouldn't notice it from Earth for over 8 minutes. F.There would be a noticeable delay in communications at the speed of light between Earth and astronauts on the Moon.

We can sketch light rays, as shown here, to understand how the water lens affects the appearance of the arrow viewed through it. One light ray comes from the head of the arrow, and another from its base: both are bent (refracted) through the water lens as they pass through it. Your eye then sees the light from the head and base of the arrow coming through the glass in different places, and the arrow looks different to you. Experiment by moving your eye and the arrow according to the three configurations shown below. Note how the relative size and orientation of the arrow appears to change at each position, as compared to its appearance when it is not viewed through the water lens. Based on your results, place each of the listed effects at the location your eye observes them on the diagram.

C. Inverted larger arrow B. Inverted smaller arrow A. Smaller arrow, not inverted

Watch the first section, and click through, using the "Play" button until you reach Section 2 of 3. Here we will explore the following questions: How many properties does a wave have? Are any of these related to each other? Work your way through to the experimental section, where you can adjust the properties of the wave. Watch the simulation for a moment to see how fast the frequency counter increases. Reset the simulation, and increase the frequency. Did the wavelength change in the expected way based on the relationship between wavelength and frequency?

C. Yes. The wavelength decreased as expected.

Why is the Hubble Space Telescope in space instead of on the ground?

Choose one or more: A. It avoids atmospheric distortion. C. It observes in the UV.

Which of the following can be observed from Earth's surface?

Choose one or more: A. visible light D. radio waves

A light wave does not require:

D. a medium.

The advantage of an interferometer is that

D. the resolution is dramatically increased.

Place the names of the types of radiation in their correct places in the EM spectrum. (You may have to scroll to see all options.)

F. Gamma rays E. X-rays C. Ultraviolet A. Visible light D. Infrared G. Microwaves B. Radio

Match each telescope component with its ocular equivalent. You may need to use the scrollbar to view all of the categories.

Pupil: - Aperture Retina: - CCD Optic nerve: - Wiring to computer Lens: - Objective lens Iris: - (blank)