Try Answering These

1. Bees have eyes that see ultraviolet radiation as well as visible light. If you were a flower who wanted only bees and not moths to visit you, what could you do to make sure bees (and not moths) get the message?

   Answer: Since flowers and bees evolved together, they each depend on being able to find each other. Therefore, they advertise using patterns on their petals that only bees can see.

2. Snakes' eyes are sensitive to infrared radiation. This makes them good hunters at night in the dark. Why?

   Answer: Because the body temperature of most animals that snakes hunt is in the range of 37 degrees C, the peak wavelength of light that they give out is in the infrared. At night, without the benefit of daylight shining on an animal, the snake can see its prey by the infrared light it gives off. Rattlesnakes have two sets of eyes. One set that we identify as regular eyeballs is used for detecting things in visual light. Another pair located below its regular eyes is sensitive to infrared light.

3. The Sun puts out most of its light at visible wavelengths. As creatures on earth evolved, they developed eyes that respond to the short wavelengths of visible light. Imagine that you are a being on a planet whose Sun puts out most of its light at radio wavelengths, and you don't see the wavelengths of light visible to us on Earth. Do you think you would see the "colors" of radio light?

   Answer: Light in the visible spectrum is broken into different wavelengths that we see as color. If we lived on a radio light world and had the ability to see radio waves, we would probably describe them as colors. Radio light just like visual light is broken into different wavelengths. It ranges from a few centimeters to six football fields in length. We would need to have a very different set of eyes to detect such waves in any detail.

4. Our atmosphere is turbulent--wind and heat from the ground move the air around. This causes the light from stars to twinkle when we look at them from the ground. Do planets twinkle?

   Answer: Have you ever seen a pencil sticking out of a glass of water? The part in the water shifts position from the part in the air because of refraction. If you stir the water up, then you'll see the image of the pencil through the water move around. This is like what happens to starlight when it passes through our atmosphere if the air is moving around a lot. It causes the star's light to move around just a little. This is twinkling. We see the planets in the night sky being brighter than the stars. And also, the planets are so much closer to us than stars, so the planets are really little disks from our view whereas the stars are points of light. The larger the disk, the more the image resists twinkling. When the atmosphere is particularly turbulent, though, planets seem to twinkle, too--especially when low on the horizon where the light has to travel through more air to reach the ground.

5. Humans are nearly blind to most wavelengths of light. If you lost your ability to see visible light, but could choose another wavelength region of the electromagnetic spectrum, what would you choose? Describe how you would see the world around you.

   Answer: ANSWERS WILL VARY. For example, a possible choice is infrared; in that case, the student would see most mammals and birds and hot rocks that soak up sunshine and then re-emit the light in the infrared.

6. How would you prepare yourself to view the light from a solar eclipse as compared to the light coming from a lunar eclipse?

   Answer: A lunar eclipse can be viewed without any special precautions. The shadow that you see moving across the lunar surface is made by the Earth blocking the sunlight. Why do you see the moon at all? After all, the moon does not give off optical light since it is far too cold. You see the moon because Sunlight reflects off its surface. During a lunar eclipse the moon crosses the shadow that the Earth makes.

   A solar eclipse happens when the moon moves in front of the Sun, relative to us on Earth. Looking at a solar eclipse with your naked eyes is the same as looking at the Sun. Not all the Sunlight is blocked during a full eclipse, and if you are looking at it when the Sun first starts to reappear, you can burn the light-sensitive tissue in your eye, the retina. Damage caused to the retina by looking at the Sun is permanent.

7. The water molecules in our atmosphere stop infrared rays that come from the Sun and other stars. If you built a telescope on the ground to study infrared light coming from distant stars, where would you locate it and why?

   Answer: The higher you go in the atmosphere, the less water there is. Astronomers reduce the amount of atmospheric water they have to look through by constructing infrared telescopes in high mountains, such as the Keck Observatory in Hawaii at 14,000 ft. Another solution is to put infrared telescopes in space, like IRAS in the 1980's and SIRTF to come soon.