How does a Beam of Light Travel? What does this activity tell you about the path of light?

Electromagnetic Waves An ELECTROMAGNETIC WAVE is a transverse wave that transfers electrical and magnetic energy. It consists of vibrating electric and magnetic fields that move through space at the speed of light! Produced by charged particles that make a magnetic field, which exerts magnetic forces.

Electromagnetic Radiation ELECTROMAGNETIC RADIATION - the energy that is transferred through space by electromagnetic waves. THE SPEED OF LIGHT- All electromagnetic waves travel at the same speed in a vacuum – about 300,000 km per second The sun’s light takes 8 minutes to travel the 150 million km to Earth.

Wave Model of Light POLARIZED LIGHT– The light that passes through and vibrates in only one direction of a polarizing filter.

Particle Model of Light When a beam of light shines on some substances, it causes electrons to move, creating a flowing electric current, or knocking the electron out of the substance – called the PHOTOELECTRIC EFFECT. Each packet of light energy is called a PHOTON

Waves of the Electromagnetic Spectrum All electromagnetic waves travel at the same speed in a vacuum, but they have different wavelengths and different frequencies. The ELECTROMAGNETIC SPECTRUM is the complete range of electromagnetic waves placed in order of increasing frequency. Copy the image on the next slide (including colors) into your notes.

The Electromagnetic Spectrum

Infrared Rays INFRARED RAYS are electromagnetic waves with wavelengths shorter than those of radio waves. HEAT LAMPS– You can feel the energy of infrared rays as heat. INFRARED CAMERAS – Take pictures using infrared rays instead of light, called THERMOGRAMS – an image that shows regions of different temperatures in different colors.

Radio Waves RADIO WAVES have the longest wavelengths and lowest frequency BROADCAST WAVES – Radio waves with longer wavelengths; used in broadcasting (radio, tv) MICROWAVES – Radio waves with the shortest wavelengths and highest frequencies; used in cell phones, microwave ovens, and RADAR – a system that uses reflected radio waves to detect objects and measure their distance and speed.

Visible Light VISIBLE LIGHT are electromagnetic waves that you can see. Shorter wavelengths and higher frequencies than infrared rays. White is a mixture of many colors. Longest wavelength = red

Ultraviolet Rays ULTRAVIOLET RAYS are electromagnetic waves with wavelengths that are just shorter than those of visible light. Shorter wavelengths and higher frequencies than infrared rays. Harmful; kill bacteria, can burn skin, lead to cancer, and damage eyes Small doses are useful – cause skin to make Vitamin D

X-Rays X-RAYS are electromagnetic waves whose wavelengths are just shorter than those of ultraviolet rays. Dense matter absorbs X-rays, and doesn’t allow them to pass through Over-exposure leads to cancer Used in industry and engineering

Gamma Rays GAMMA RAYS are electromagnetic waves with the shortest wavelengths and highest frequencies. Most penetrating of all waves. Produced by radioactive substances and certain nuclear reactions. Used to kill cancer cells; objects in space emit gamma rays (ex: explosion of stars)