Astronomy Week 9 Unit 22: The Electromagnetic Spectrum Lecture, Concept and Review questions

What is blackbody radiation? How is it useful to astronomers?

- Is a theoretical object that 1. Absorbs ALL light that falls upon it 2. Emits light ONLY as a result of its temperature one way for them to measure the temperature of stars is based on a star's luminosity. - The temperature of objects - Chemical composition of the stuff

What is a blackbody curve?

A graph of all types of color given off by hot glowing things.

Does all electromagnetic radiation travel at the same speed?

All electromagnetic waves travel at the same speed, but they have different wavelengths and different frequencies.

How does the way a stove burner (or any hot, glowing object) change the way it emits light as its temperature gets hotter and hotter?

An an object gets hotter, it gets bluer. It emits more light.

How does an object's blackbody curve change as its temperature changes? What does the peak of the curve tell us about the temperature of the object?

As an object gets hotter, it radiates more light and with a peak that moves toward shorter wavelengths. - Something with a LOW temperature glows with a light that has the peak of its blackbody curve at a long wavelength. The low temperature is RED. - Something with HIGH temperature glows with a light that has the peak of its blackbody curve at a short wavelength. The high temperature is blue and violet. - It tells us blackbody curves their wavelengths

Which type of light has the highest energy? The lowest?

Gamma waves have the highest frequency, and shortest wavelength and therefore, carry the greatest amount of energy. Radio waves. Energy is directly related to the frequency and inversely related to wavelength. Since radio waves have the lowest frequency and longest wavelength, they have the lowest energy.

Why do you suppose that the centers of some filled pastries grow hot in a microwave oven while their outer portions do not grow as hot?

Heat is trapped inside.

What are photons?

How does the way a stove burner (or any hot, glowing object) change the way it emits light as its temperature gets hotter and hotter? Packets of light energy.

In what ways is it possible and impossible for people to personally detect energy outside the visible spectrum?

Is possible to feel the heat. Is impossible for eyes to see physically.

Our eyes are insensitive to infrared light, but there are "infrared night-vision goggle." How do you suppose we can see infrared light with these?

It helps detect heat and therefore, people can detect objects.

Why do you suppose that when you mix together red, green, and blue paint, you get a dark gray or brown color instead of white?

Other colors are by appropriate blending of red, green and blue. To make white light, you must have the colors red, green, yellow and blue.

What are the bands of the electromagnetic spectrum from short to long wavelengths?

The entire electromagnetic spectrum can be divided into seven bands: gamma ray, X-ray, ultraviolet, visible, infrared, microwave, radio (from shortest to longest wavelength).

Which type of light travels fastest?

They all travel at the same speed

Why is it more dangerous to be exposed to a weak X-ray source than to a strong infrared source?

Weak X-ray carries great deal of energy and generated only in regions with extremely high temperatures or high energy reactions taking place and is on the inside. Infrared source is only on the surface and can be detected by heat.

Tie one end of a rope or cord to a doorknob and shake the other end. To make short-wavelength waves along the rope, how rapidly (frequently) do you shake the rope? Does it take more of your energy to make short waves or long waves? How does this compare to the energy vs. wavelength of photons?

When the wavelength is shorter, the frequency is higher. Long wavelength use less energy and short wavelength uses more energy. A photon carries an amount of energy proportional to its frequency and inversely proportional to its wavelength.

What is the relationship between wavelength, frequency, and energy for light?

as the wavelength gets shorter, the energy increases; as the wavelength gets longer, the energy decreases. The greater the energy, the larger the frequency and the shorter (smaller) the wavelength.

How are color and wavelength related?

different colors correspond to different wavelengths of light

List the different types of light that make up the electromagnetic spectrum from short wavelength to long wavelength.

gamma ray, X-ray, ultraviolet, visible, infrared, microwave, radio (from shortest to longest wavelength).

What is electromagnetic radiation?

the range of electromagnetic radiation, organized by how much energy the radiation carries.

What is meant by the electromagnetic spectrum?

the range of electromagnetic radiation, organized by how much energy the radiation carries. Describe the relationship between the wavelength, frequency, and energy of a wave. There is an inverse relationship between wavelength, frequency, and energy.