Electromagnetic Radiation and Atomic Spectra

Question 1

How can electromagnetic radiation be described

Answer 1

Electromagnetic radiation can be described in terms of waves and characterised in terms of wavelength and / or frequency

Question 2

Which equation connects velocity of light, wavelength and frequency

Answer 2

The relationship between these quantities is given by c = f λ .

Question 3

What is the electromagnetic spectrum

Answer 3

The different types of radiation arranged in order of wavelength is known as the
electromagnetic spectrum.

Question 4

What are wavelengths of visible light expressed in

Answer 4

Wavelengths of visible light are normally expressed in nanometres (nm).

Question 5

What type of nature does electromagnetic radiation have

Answer 5

Electromagnetic radiation can be described as a wave (has a wavelength and frequency), and as a particle, and is said to have a dual nature.

Question 6

What are photons

Answer 6

When electromagnetic radiation is absorbed or emitted by matter it behaves like a stream of particles. These particles are known as photons.

Question 7

What type of energy does a photon carry

Answer 7

A photon carries quantised energy proportional to the frequency of radiation.

Question 8

What happens to electrons when a photon is absorbed or emitted

Answer 8

When a photon is absorbed or emitted, energy is gained or lost by electrons within the substance

Question 9

What is the difference between photons in high frequency radiation than photons in low frequency radiation

Answer 9

The photons in high frequency radiation can transfer greater amounts of energy than photons in low frequency radiation.

Question 10

The energy associated with a single photon is given by:

Answer 10

E=hf or E=hc/λ

Question 11

The energy associated with one mole of photons is given by:

Answer 11

E = Lhf or E = Lhc/λ

Question 12

What are often the units of energy

Answer 12

kJ mol-1.

Question 13

What happens when energy is transferred to atoms

Answer 13

When energy is transferred to atoms, electrons within the atoms may be promoted to higher energy levels.

Question 14

When does an atom emit a photon of light energy

Answer 14

An atom emits a photon of light energy when an excited electron moves from a higher energy level to a lower energy level.

Question 15

What does the light energy emitted by an atom produce

Answer 15

The light energy emitted by an atom produces a spectrum that is made up of a series of lines at discrete (quantised) energy levels. This provides direct evidence for the existence of these energy levels.

Question 16

What does each element in a sample produce

Answer 16

Each element in a sample produces characteristic absorption and emission spectra. These spectra can be used to identify and quantify the element.

Question 17

In absorption spectroscopy what is em radiation directed at

Answer 17

In absorption spectroscopy, electromagnetic radiation is directed at an atomised sample. Radiation is absorbed as electrons are promoted to higher energy levels.

Question 18

How is an absorption spectrum produced

Answer 18

An absorption spectrum is produced by measuring how the intensity of absorbed light varies with wavelength.

Question 19

In emission spectroscopy what are high temps used for

Answer 19

In emission spectroscopy, high temperatures are used to excite the electrons within atoms. As the electrons drop to lower energy levels, photons are emitted.

Question 20

How is an emission spectrum of a sample produced

Answer 20

An emission spectrum of a sample is produced by measuring the intensity of light emitted at different wavelengths.

Question 21

What is the concentration of an element in atomic spectroscopy related to

Answer 21

In atomic spectroscopy, the concentration of an element within a sample is related to the intensity of light emitted or absorbed.