Light and the Electromagnetic Spectrum

Light Phenomenon Isaac Newton ( ) believed light consisted of particles By 1900 most scientists believed that light behaved as a wave.

The Electromagnetic Spectrum The electromagnetic spectrum represents the range of energy from low energy, low frequency radio waves with long wavelengths up to high energy, high frequency gamma waves with small wavelengths.

Visible light is a small portion of this spectrum. This is the only part of this energy range that our eyes can detect. What we see is a rainbow of colors. R ed O range Y ellow G reen B lue I ndigo V iolet ROY G BIV

The colors we see in objects are the colors that are reflected, all other colors are absorbed. A red t-shirt appears red because red is reflected to our eyes and the other colors are absorbed. When all colors are being reflected we see white light (white isn’t really a color)

When all wavelengths of light are being absorbed we see black (black also, isn’t really a color)

Absorption and Transmission Waves that are not reflected are either absorbed OR They are transmitted (pass through the substance) like light through a glass window or a pair of glasses

Refraction

Rainbows are Refracted Light When light waves from the sun pass through a droplet of water in the air, the light is refracted. The different colors of light travel at different speeds through the drop therefore the colors are refracted by different amounts= RAINBOW

Electromagnetic Waves Do not need a medium, CAN travel through empty space! Electromagnetic waves (light waves, microwaves, x-rays) can travel through empty space

TRANSVERSE WAVES Transverse waves move perpendicularly to the direction the wave is moving Transverse waves are made up of CRESTS and TROUGHS Electromagnetic waves are examples of transverse waves.

Properties of a Wave 1) AMPLITUDE 2) WAVELENGTH 3) FREQUENCY 4) SPEED

Comparing Waves The frequency (v) of a wave is the number of waves to cross a point in a specified unit of time The wavelength- the distance from crest to crest on a wave Amplitude is the greatest distance a wave moves away from the rest position; the greater the distance the more energy

Wavelength The distance between any 2 corresponding points on a wave

Amplitude

Wavelength vs Frequency

Properties of a Wave

Reflection When a wave hits an object through which it cannot pass, it bounces back. This is called REFLECTION All waves can be reflected

The Law of Reflection Angle of incidence = Angle of reflection In other words, light gets reflected from a surface at the same angle it hits it. The same !!!

Refraction REFRACTION is the bending of waves when waves move from one medium to another. When a wave hits a new medium, it changes speed and the wavelength changes