HW #7

X rays, because they have more energy, travel through space faster than visible light.

False

Why is a sunflower yellow?

It reflects yellow light.

How are wavelength, frequency, and energy related for photons of light?

Longer wavelength means lower frequency and lower energy.

Which of the following procedures would allow you to make a spectrum of the Sun similar to the one shown, though with less detail?

Pass a narrow beam of sunlight through a prism.

The diagrams below are the same as those from Part A. This time, rank the atoms based on the wavelength of the photon emitted as the electrons change energy levels, from longest to shortest.

Shortest Arrow = from outer edge to center 3rd Shortest Arrow = second closest ring to the outer edge to center 2nd Longest Arrow = middle circle to center Longest Arrow = outer edge to middle circle

Which of the following best describes why the Sun's spectrum contains black lines over an underlying rainbow?

The Sun's hot interior produces a continuous rainbow of color, but cooler gas at the surface absorbs light at particular wavelengths.

Any spectrum can be displayed either in photographic form as shown to the left or as a graph. Which of the following graphs could represent a portion of the Sun's visible light spectrum?

The one that dips down.

Listed following are various physical situations that describe how light interacts with matter. Match these to the appropriate category.

Transmission -Cell phone signals pass through walls. -Visible light meets clear glass. Absorption -Visible light does not pass through a black wall. -Blue light hits a red sweatshirt. Reflection or scattering -White light hits a white piece of paper. -Red light hits a red sweatshirt Emission -Light comes from a light bulb. -Light comes from your computer screen.

Lines of a particular element appear at the same wavelength in both emission and absorption line spectra.

True

The energy levels for electrons vary from one element to another.

True

Study the graph of the intensity of light versus wavelength for continuous spectra, observing how it changes with the temperature of the light bulb. Recall that one of the laws of thermal radiation states that a higher-temperature object emits photons with higher average energy (Wien's law). This law is illustrated by the fact that for a higher temperature object, the graph peaks at __________.

a shorter wavelength

If you heat a rock until it glows, its spectrum will be:

a thermal radiation spectrum.

What type of visible light spectrum does the Sun produce?

an absorption line spectrum

The absorption line spectrum shows what we see when we look at a hot light source (such as a star or light bulb) directly behind a cooler cloud of gas. Suppose instead that we are looking at the gas cloud but the light source is off to the side instead of directly behind it. In that case, the spectrum would __________.

be an emission line spectrum

Compared to the Sun, a star whose spectrum peaks in the infrared is:

cooler

We divide the electromagnetic spectrum into six major categories of light, listed below. Rank these forms of light from left to right in order of increasing wavelength. To rank items as equivalent, overlap them.

gamma rays X rays ultraviolet visible light infrared radio waves

Blue light has higher frequency than red light. Thus, blue light has:

higher energy and shorter wavelength than red light.

Rank the forms of light from left to right in order of increasing speed. To rank items as equivalent, overlap them.

infrared, visible light, gamma rays, ultraviolet, radio waves, X rays ALL THE SAME SPEED

In the illustration of the solar spectrum, the upper left portion of the spectrum shows the __________ visible light.

lowest frequency

Click "show" for the emission line spectrum, then click "choose gases" and study the emission line spectrum for neon. The neon "OPEN" sign appears reddish-orange because __________.

neon atoms emit many more yellow and red photons than blue and violet photons

Rank the forms of light from left to right in order of increasing frequency. To rank items as equivalent, overlap them.

radio waves infrared visible light ultraviolet X rays gamma rays

Rank the forms of light from left to right in order of increasing energy. To rank items as equivalent, overlap them.

radio waves infrared visible light ultraviolet X rays gamma rays

Notice that the Sun's spectrum appears brightest (or most intense) in the yellow-green region. This fact tells us __________.

the approximate temperature of the Sun's surface

When an atom absorbs a photon containing energy, any of the following can happen except which?

An electron moves from an upper energy level to a lower one.

Suppose we want to know what the Sun is made of. What should we do?

Compare the wavelengths of lines in the Sun's spectrum to the wavelengths of lines produced by chemical elements in the laboratory.

The diagrams below show the same set of energy levels as in Parts A and B, but with a different set of electron transitions (notice that the arrows are now different). Assuming that these electron transitions were caused by the absorption of a photon, rank the atoms based on the energy of the absorbed photon, from highest to lowest.

Highest Arrow = from center to outer edge 2nd Highest Arrow = the outer edge to center to second closest ring 3rd Highest Arrow = center to middle circle Lowest Arrow = middle circle to outer edge

The circles in the diagrams below represent energy levels in an atom, and the arrows show electron (blue dot) transitions from one energy level to another. (The spacing between circles represents differences in energy: A larger spacing means a greater difference in energy.) Assuming that the transitions occur as photons are emitted, rank the atoms based on the photon energy, from highest to lowest.

Highest Arrow = from outer edge to center 2nd Highest Arrow = second closest ring to the outer edge to center 3rd Highest Arrow = middle circle to center Lowest Arrow = outer edge to middle circle