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PHYSICS Mr. BALDWINWAVES 12-Feb-14

AIM: What is light? What is the electromagnetic (E-M) spectrum?

DO NOW: What are the colors of the rainbow?Why are they different?How is it that heat comes to us from the Sun?

Homework: Worksheet 24.1 - The Electromagnetic Spectrum

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Electromagnetic Waves

• The electromagnetic spectrum consists of all types of electromagnetic radiation

• Gamma rays, x-rays, ultraviolet radiation, visible light, infrared radiation, millimeter waves, microwaves, and radio waves are all electromagnetic waves that differ only in their frequencies & wavelengths.

• ALL Electromagnetic waves travel in a vacuum with the same speed of light. (300,000,000 m/s)

• Write this in scientific notation.

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Electromagnetic Spectrum

• Infrared radiation (IR)– created by molecular

vibrations

• Visible light (white light)– created by electron excitation

• Ultraviolet radiation (UV)– created by electron excitation

• X-ray radiation– created by high energy

electron excitation

• Gamma (γ) radiation – created within the atomic

nuclei by high energy nuclear processes

• Ionization Radiation is any radiation that is energetic enough to ionize biological matter.– Causes genetic mutation of

DNA– Penetrate deep into matter

• As λ decreases, the f increases, and hence the energy E increases

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Components of Visible Light

• White light is polychromatic:–Made up of different colors of light– RedOrangeYellowGreenBlueIndgoViolet

• Wavelength Range of visible lightl 400 – 700 nm (Nanometer: 1nm = 10–9m

• Write these values in scientific notation in meters• Determine the Frequency Range of visible light• f: 4.3 – 7.5 x 1014Hz

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BALDWIN 7

PHYSICS Mr. BALDWINGEOMETRIC OPTICS 13-Feb-14

AIM: How does light behave when it is incident on another medium?

DO NOW: Write a short paragraph on what you observe when a pencil or spoon is placed in a clear glass of water.

HOME WORK – Read up on Geometric Optics

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Reflection; Refraction• Reflection: the return or

change in direction of a wave (light or sound) at the same angle is called reflection

– Echo is sound reflected

• Refraction: the change in direction and speed of a wave as it passes from one medium to another

– Bending of light as it passes through a prism

Reflection: Law of Reflection

Law of reflection: the angle of reflection (that the ray makes with the normal to a surface) equals the angle of incidence.

angle of incidence = angle of reflection

ri

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Refraction: Snell’s Law

Light changes direction (bends) when crossing a boundary from one medium to another. This is called Refraction. The angle the outgoing ray makes with the normal is called the angle of refraction.

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Light slows when traveling through a medium. The index of refraction of the medium is the ratio of the speed of light in vacuum to the speed of light in the medium: