OZ.2

Question 1

Which part of the electromagnetic spectrum is the most damaging to skin?

Answer 1

Ultraviolet

Question 2

What effect can visible light have on skin?

Answer 2

Temporary reddening.

Question 3

What effect can low frequency ultraviolet (UV-A) have on skin?

Answer 3

Quick tanning which fades away quickly.

Question 4

What effects can high frequency ultraviolet (UV-B/UV-C) have on skin?

Answer 4

Tanning and sunburning.

Question 5

The higher the frequency of the electromagnetic wave the higher the risk of getting what and why?

Answer 5

The risk of getting skin cancer is higher with higher frequencies because it corresponds to the energy required to break bonds including molecules such as DNA, causing cancer.

Question 6

In which region of the atmosphere does most ultraviolet absorption take place?

Answer 6

In the stratosphere.

Question 7

Which is the most important ultraviolet-absorbing gas in our atmosphere?

Answer 7

Ozone, O3.

Question 8

What frequencies of ultraviolet does ozone absorb?

Answer 8

10 x 10^14 - 14 x 10^14 Hz, (UV-B and UV-C).

Question 9

What are negative effects of UV-B and UV-C radition if too much of it reacher the earth’s surface?

Answer 9

DNA damage which leads to skin cancer, eye damage which could lead to cataracts, damage crops.

Question 10

Is it good to have ozone in the troposphere and why?

Answer 10

No, ozone at ground level in the troposphere is a significant pollutant because ozone is involved in the reactions producing photochemical smog which causes haziness and respiratory problems in people.

Question 11

What happens to molecules in the stratosphere because of high energy ultraviolet radiations?

Answer 11

Simple molecules are broken down by the radiation and some covalent bonds would break to give radicals.

Question 12

What are radicals?

Answer 12

Radicals are atoms or molecules with at least one unpaired electrons.

Question 13

What happens to molecules, atoms and radicals even higher up in the ionosphere?

Answer 13

With the radiations having even more energy, they are powerful enough to knock electrons off atoms, molecules and radicals, producing ions.

Question 14

What characteristic of light is the same for all kinds of electromagnetic radiation?

Answer 14

The speed of light (c). It has a value of 3 x 10^8 m/s in vaccum.

Question 15

What is the equation linking speed of light, frequency and wavelength?

Answer 15

Speed of light = wavelength x frequency

Question 16

What is the equation that links the energy of a photon of light, plank constant and frequency?

Answer 16

Energy of a photon of light = Plank constant x frequency

Question 17

What are four different aspects of behaviour associated with energy?

Answer 17

• Translation (the molecule moving around as a whole)
• Rotation (of the molecule as a whole)
• Vibration of bonds
• Electron energy

Question 18

What is electronic energy?

Answer 18

Is the energy associated with changes when an electron in an atom or molecule moves from one level to another. It is quantised.

Question 19

Which region of electromagntic radiation corresponds to vibrational energy change?

Answer 19

Infrared.

Question 20

Which region of electromagnetic radiation corresponds to rotational energy changes?

Answer 20

Microwave.

Question 21

Which region of electromagnetic radiation corresponds to electronic energy change?

Answer 21

Visible light and ultraviolet.

Question 22

Why are energy changes associated with different behaviours given in ranges rather than a specific value?

Answer 22

Because the energy change also depends on the substance involved. Some substance have stronger bonds which will require more energy to do the same thing as a substance with a weaker bond.

Question 23

What are three things that can happen when a molecule absorbs visible light/ultraviolet radiation?

Answer 23

1. Electrons can be excited to a higher energy level.
2. Molecule can absorb lots of energy and break, known as photochemcial dissociation, when bonding electrons can no longer bond the atoms together and radicals are formed.
3. With enough energy, molecules may have so much energy that an electron is abke to leave it, and then we say the molecule is ionised.