Name ______Date ______Class ______

Modern Chemistry • CHAPTER 1

HOMEWORK 4-2

Multiple Choice. Place the letter of the best answer in the blank.

_____1. In some ways, light behaves as an electromagnetic wave. This means that, as the wavelength of light increases, its frequency ___.

  1. Remains the same.
  2. Increases.
  3. Decreases.
  4. Becomes equal to the speed of light.

_____2. Planck proposed the existence of quanta when he observed that

  1. frequency and wavelength are mathematically related to one another.
  2. Light moves more quickly through a vacuum than it moves through air.
  3. Electrons in some metals are bound more or less tightly than electrons in other metals.
  4. A hot object does not emit electromagnetic energy continuously.

_____3. What do emission spectra show?

  1. the frequencies at which light is given off from excited electrons.
  2. The frequencies at which light is absorbed by electrons.
  3. The structure of the atoms of any element that exists as a gas.
  4. The speed with which a substance emits electromagnetic waves.

_____4. Match each term describing waves to its definition.

_____ amplitudeA. the distance between two crests

_____wavelengthB. the wave’s height from the origin to the crest

_____frequencyC. the number of wave cycles to pass a given point per unit of time.

Short Answer.

1. Describe the relationship between the wavelength and frequency of light.

______

2. Describe the relationship between the energy of a quantum of radiation and the frequency of the radiation.

______

3. Light consists of electromagnetic waves. What kinds of visible and invisible radiation are included in the electromagnetic spectrum?

______

______

4. What happens when an electric discharge is passed through the gas or vapor of an element?

______

______

5. What is the photoelectric effect?

______

6. Label the parts of the wave shown in this drawing. Label the wavelength (), the amplitude (A), the crest (C), the trough (T), and the origin (O).

7. The product of the frequency and the wavelength always equals a(n) ______, the speed of light.

8. The units of frequency are usually cycles per second. The SI unit of cycles per second is called a(n) ______.

9. When sunlight passes through a prism, the different wavelengths separate into a(n) ______of colors.

10. Put the visible colors in order from light with the longest wavelength and lowest frequency(1) to light with the shortest wavelength and the highest frequency (7).

______orange

______green

______blue

______violet

______yellow

______indigo

______red

______11. The electromagnetic spectrum consists of radiation over a broad band of wavelengths. ______What type of radiation has the lowest frequency? What type has the highest frequency?

______12. Passing the light emitted by an element through a prism gives the ___ of the element.

______13. Planck showed mathematically that the amount of radiant energy (E) absorbed or emitted by a body is ___ to the frequency of the radiation: E = hf.

______14. What is a small, discrete unit of energy called?

______15. What did Albert Einstein call the quanta of energy that is light?

______16. What is the lowest energy level of an electron called?

______17. Only electrons in transition from ___ to ___ energy levels lose energy and emit visible light.