Electromagnetic Radiation and Light Waves

Let’s Review Rutherford’s Atom The atom has a small dense nucleus which – Contains most of the mass of the atom – Is positively charged – Contains protons (+1 charge) – Contains neutrons (no charge) The remainder of the atom – Contains most of the volume of the atom – Is mostly empty space – Contains electrons (-1 charge)

Electromagnetic Radiation Electromagnetic radiation is when radiant (light) energy is transmitted from one place to another in a wavelike pattern. There are many examples of electromagnetic radiation. – Light from the sun – X-rays used to make images of bones – Microwaves cooking food – Radio waves transmitting music

Wavelengths Electromagnetic Radiation travels in waves A wavelength is the distance between two consecutive wave peaks. A wavelength is represented by the greek letter lambda.

How are wavelengths different? Different wavelengths have different amounts of electromagnetic radiation.

Visible Light Some wavelengths can be seen as colors and these are known as visible light.

Light Light is how we can visualize electromagnetic radiation as a wave that carries energy through space. BUT Light doesn’t always behave as a wave. Another way to picture a beam of light traveling through space is as a stream of tiny packets of energy called PHOTONS.

How are the types of light different? A light wave has two factors which affect how much electromagnetic radiation (or energy) it contains. 1.Frequency: How many wave peaks pass a certain point per a given time period. 2.Speed: How fast a given peak travels.

Wave Frequency The red light wave has a smaller frequency and thus it contains less energy. The blue light wave has a larger frequency and thus it contains more energy.

Atoms Atoms can give off light. They first must receive energy. Then the energy is released in the form of a photon (packet of light energy). For example: Atoms, when exposed to heat from a flame, release energy by emitting visible light of specific colors (or specific wavelengths).

Atoms releasing Light The heat from the flame causes the atom to absorb energy or become EXCITED. Some of this excess energy is then released as light.

Atoms releasing Light Lithium emits red light Copper emits green light Sodium emits a yellow-orange light The color of light emitted corresponds to the different amounts of energy that are released.

Flame Tests By placing different elements (atoms) in a Bunsen burner flame, one can determine how much energy is being released by the color of flame.