Energy of a photon

Light and Electrons

Visible light is a kind of electromagnetic radiation (form of energy that exhibits wavelike behavior as it travels through space).

Properties of Light

• Other examples include X-rays, ultraviolet and infrared light, microwaves, and radio waves.

• The electromagnetic spectrum consists of all types of electromagnetic radiation

Properties of a Wave

All forms of electromagnetic radiation move at a speed of 3.0 x 10⁸ m/s through air.

• Wavelength – λ (m, cm, or nm) and frequency – ν (wave/second) are measurable properties of wave motion.

  • One wave/second is called a hertz (Hz).

• The relationship between wavelength (λ) and frequency (ν) is c = λν where c = speed of light.

Multiple Choice

How many valence (outer) electrons does an Oxygen atom have?

• 2

• 6

• 8

• 16

Atomic Emission Spectra

Ground state of an atom is the lowest energy state of the atom. When those atoms are given energy, the electrons absorb the energy and move to a higher energy level.

Atomic Emisions Spectra

Excited state of an atom is a state where its potential energy is higher than the ground state.

An atom in the excited state is not stable. When it returns back to the ground state, it releases the energy that it had previously gained in the form of electromagnetic radiation

Multiple Choice

To jump to an excited state the electron must____

• emit energy

• absorb energy

Multiple Choice

An electron in an excited state is _____

• STABLE

• NOT STABLE

Multiple Choice

When the electron fall down from an excited state, it ___

• absorbs photon of energy

• releases photon of energy

Multiple Choice

When an electron ABSORBS energy:

The electron moves from a ____energy level to a____ energy level

• higher / lower

• lower / higher

Multiple Choice

When an atom emits a photon of light, the electron jumps from a ____ energy level to a ____ energy level

• higher / lower

• lower / higher

Let's work on the practice problems!

Write the following equations down in your notes:

Tape the paper into your notebooks.

Problem #1

Multiple Choice

What is the given?

• frequency

• engergy

• wavelength

Multiple Choice

What is the unknown?

• frequency

• engergy

• wavelength

Given: frequency (v)

Unknown: energy (E)

Once you choose the equation, plug in the numbers.

​What equation should you use?

E = hv

Do problem #2

Problem #3

Multiple Choice

What is the given?

• frequency

• engergy

• wavelength

Multiple Choice

What is the unknown?

• frequency

• engergy

• wavelength

Given: wavelength (λ)

Unknown: energy (E)

Once you choose the equation, plug in the numbers.

​What equation should you use?

Problem #4

Problem #5

*solve for energy in J NOT kJ

Problem #6

Problem #7

Use the following equation: E = hv

Isolate v.

Problem #8