Flame Lab Primer

Flame Lab Primer

Electromagnetic radiation is composed of transverse waves oscillating in the electric
and magnetic fields (through space or matter). These waves are characterized by their
wavelength (λ) and frequency (ν). Wavelength is defined as the distance between
successive crests (or troughs) on a wave, and is measured in meters. Frequency is
defined as the number of waves that pass a given point per second, and is measured
in 1/seconds, or Hertz (Hz).

All electromagnetic waves travel at the speed of light (c), or 2.998×10⁸ m/s

Multiple Choice

What kind of waves comprise the electromagnetic spectrum?

• transverse

• compression

• longitudinal

Open Ended

How are wavelengths measured?

I am not asking for units.

Open Ended

Define frequency.

Multiple Choice

Frequency is measured in

• Hertz

• meters per second

• meters

• seconds

The relationship between the wavelength, frequency and speed of an electromagnetic
wave is given by the equation: c=λν
c being the speed of light
λ being the wavelength
ν being frequency

Electromagnetic radiation also occurs as discrete packets of energy (or quanta) called
photons. Photons are also called light particles and are the fundamental unit of electromagnetic energy. The energy per photon (in Joules) is given by the equation: Ephoton=hν
h=Planck’s constant, which has a value of 6.626×10^-34J⋅s

Visible light is the most familiar example of electromagnetic radiation. Differences in
the wavelengths of visible light are manifested as different colors, shown in the Color
Spectrum below. Other examples of electromagnetic radiation include X-rays, ultraviolet
light, infrared light, microwaves and radio waves.

Visible light and all radiation on the electromagnetic spectrum moves at the speed of light (c). Light travels at 2.998x10⁸ m/s

Multiple Select

What is a photon?

Select all that apply

• a light particle

• a discrete packet of energy

• a type of torpedo

• a quark

Multiple Select

What does "c" equal?

select all apply

• the speed of light

• the speed of everything on the electromagnetic spectrum

• 2.998×10⁸m/s

• 299,800,000 meters per second

So, how does electromagnetic radiation relate to flame tests?

When an atom (or ion) absorbs energy, its electrons can make transitions from lower
energy levels (ground state) to higher energy levels (excited state). The energy absorbed could be in the form of heat (as in flame tests), or electrical energy, or electromagnetic radiation.

When electrons subsequently return from higher energy levels to lower energy levels, energy is released predominantly in the form of electromagnetic radiation (photons).

The spacing between energy levels in an atom determines the sizes of the transitions
that occur, and thus the energy and wavelengths of the collection of photons emitted:

Multiple Choice

higher energy = shorter wavelengths

• true

• false

If emitted photons are in the visible region of the spectrum, they may be perceived as lines of
different colors (note: that photons outside the visible spectrum may also be emitted, but
cannot be seen by eye). The result is called a line emission spectrum, and can serve as a
‘fingerprint’ of the element to which the atoms belong. For example, the line spectra shown
below for the elements helium and carbon are clearly quite different.

Unfortunately, techniques more sophisticated than those used in this lab are required to
obtain such line spectra. To the naked eye, when an element is vaporized in a flame (or an
electrical discharge) the emission spectrum will appear to be just one color. For example,
helium gas when excited by an electrical discharge emits light that appears an orange-peach
color. This one color results from a combination of all lines of the emission spectrum, in
proportion to their intensities. As many elements will still produce distinctive colors under
such conditions, simple flame tests can be used to identify these elements. In fact, flame
tests were used to identify elements long before the invention of modern techniques,
such as emission spectroscopy.

Dropdown

The orange peach color of helium​

Select answer

the result of combination of ​

Select answer

lines of the emission spectrum, ​

Select answer

their intensities

Multiple Choice

Are all photons visible light?

• No, photons exist across the entire electromagnetic spectrum

• Yes, photons are only visible light

• No, this is definitely not the correct answer

• This one is also wrong

Match

Use the image to put the colors on order from least (left) to most energy (right)

• red

• orange

• green

• blue

• violet

least energy

2nd least energy

moderate energy

2nd most energy

most energy

• least energy

• 2nd least energy

• moderate energy

• 2nd most energy

• most energy

Open Ended

In your own words explain the relationship between wavelength and frequency.

Open Ended

In your own words explain what is happening to the energy of visible light as you move from red to violet.