April 26, 2017 Sit with your class (3rd period first two rows, 4th period second two rows, and 5th period third two rows) Start the packet (first 3 pages – don’t start the crossword yet). SHARE the calculators, rulers, and protractors – only have one tool at a time, and when you are done, pass it to someone else

Light Interactions and Light in Our World

Light Interactions The law of reflection states that the angle of incidence is equal to the angle of reflection. Things that are luminous can be seen because they produce their own light. Things that are illuminated can be seen because light reflects off them. Absorption is the transfer of light energy to particles of matter. Scattering is an interaction of light with matter that causes light to change direction.

Light Interactions Refraction of light waves can create optical illusions and can separate white light into separate colors. Diffraction depends on the light’s wavelength. Light waves diffract more when traveling through a narrow opening. Interference can be constructive or destructive. Interference of light waves can cause bright and dark bands.

Diffraction & Interference

Absorption & Scattering

Do You See What I See?

Mirrors & Lenses Rays are arrows that show the path of a single light wave. Ray diagrams can be used to find where images are formed by mirrors and lenses. Plane mirrors and convex mirrors produce virtual images. Concave mirrors produce both real images and virtual images. Convex lenses produce both real images and virtual images. Concave lenses produce only virtual images.

Law of Reflection: angle of incidence = the angle of reflection

How Images Are Formed in Plane Mirrors This is a virtual image because it is right side up How Images Are Formed in Plane Mirrors

Optical Axis, Focal Point, Focal Length

Concave Mirrors “Cave in” Converge light Create real or virtual images

Concave Mirrors

Convex Mirrors

Convex Mirrors Curved outward Spreads out light Virtual images Allows wider images “Objects in mirror are closer than they appear”

Refraction

Refraction

How Light Passes Through Lenses

Convex Lens Thicker in the middle, thinner on the edges Converging rays Can make a real (upside down and can be projected) image Can make a virtual image (right side up) Can magnify

Convex Lenses

Concave Lens Thinner in the middle, thicker on the edges Concave “caves” in Diverging rays Makes only virtual images Makes something look smaller

Concave Lenses

Fun With Color

Polarizing Lenses

The Eye The human eye has several parts, including the cornea, the pupil, the iris, the lens, and the retina. Nearsightedness and farsightedness happen when light is not focused on the retina. Both problems can be corrected with glasses or eye surgery. Color deficiency is a condition in which cones in the retina respond to the wrong colors. Eye surgery can correct some vision problems.

What is light? Light is an electromagnetic (EM) wave. An EM wave is a wave that consists of changing electric and magnetic fields. EM waves require no matter through which to travel. EM waves can be produced by the vibration of charged particles. The speed of light in a vacuum is about 300,000,000 m/s. EM waves from the sun are the major source of energy for Earth.

The Electromagnetic Spectrum All electromagnetic (EM) waves travel at the speed of light. EM waves differ only by wavelength and frequency. The entire range of EM waves is called the electromagnetic spectrum.

Radio waves are used for communication. AM means amplitude modulation FM means frequency modulation PhET Simulation

Microwaves are used in cooking and in radar. PhET Simulation

The absorption of infrared waves is felt as an increase in temperature.

Visible Light Visible light is the narrow range of wavelengths that humans can see. Different wavelengths are seen as different colors.

Ultraviolet Light Killing bacteria Producing vitamin C Can cause sunburns

Bees see UV light… So they see the world differently than we do!

X-Rays

Gamma Rays

Light & Color Objects are transparent, translucent, or opaque depending on their ability to transmit light. Colors of opaque objects are determined by the color of light that they reflect. Colors of translucent and transparent objects are determined by the color of light they transmit. White light is a mixture of all colors of light. Light combines by color addition. The primary colors of light are red, blue, and green. Pigments give objects color. Pigments combine by color subtraction. The primary pigments are magenta, cyan, and yellow.

Objects are transparent, translucent, or opaque depending on their ability to transmit light.

Colors of opaque objects are determined by the color of light that they reflect.

Colors of translucent and transparent objects are determined by the color of light they transmit.

Light combines by color addition Light combines by color addition. The primary colors of light are red, blue, and green.

Pigments combine by color subtraction.

The primary pigments are magenta, cyan, and yellow.

Question 1 A wave has a low speed, but a high frequency. What can be inferred about its wavelength? A. The distance a wave will vibrate from its resting point. B. The wavelength will be very long C. It depends on how fast the speed is D. The wavelength will be short

Answer 1 A wave has a low speed, but a high frequency. What can be inferred about its wavelength? A. The distance a wave will vibrate from its resting point. B. The wavelength will be very long C. It depends on how fast the speed is D. The wavelength will be short

Question 2 How is amplitude related to energy? A. The larger the amplitude, the more energy a wave carries B. The larger the amplitude, the less energy a wave carries C. The shorter the amplitude, the more energy a wave carries D. Amplitude is not related to energy

Answer 2 How is amplitude related to energy? A. The larger the amplitude, the more energy a wave carries B. The larger the amplitude, the less energy a wave carries C. The shorter the amplitude, the more energy a wave carries D. Amplitude is not related to energy

Question 3 Which electromagnetic waves is the eye able to see? Red, green, and ultraviolet Red, infrared, and yellow Blue, green, and ultraviolet Orange, green, and red

Question 3 Which electromagnetic waves is the eye able to see? Red, green, and ultraviolet Red, infrared, and yellow Blue, green, and ultraviolet Orange, green, and red

Question 4 Ultraviolet light has a higher frequency than infrared light has. Which statement about visible light is true? A. Blue light has a longer wavelength than orange light has. B. Green light has a higher frequency than violet light has. C. Yellow light has a shorter wavelength than blue light has. D. Red light has a lower frequency than green light has.

Answer 4 Ultraviolet light has a higher frequency than infrared light has. Which statement about visible light is true? A. Blue light has a longer wavelength than orange light has. B. Green light has a higher frequency than violet light has. C. Yellow light has a shorter wavelength than blue light has. D. Red light has a lower frequency than green light has.

Question 5 Which light interaction explains why you can see things that do not produce their own light? A. absorption B. reflection C. refraction D. scattering

Answer 5 Which light interaction explains why you can see things that do not produce their own light? A. absorption B. reflection C. refraction D. scattering

Question 6 What is the distance between two adjacent wave compressions? A. 1 m/s B. 1 wavelength C. 1 Hz D. 1 amplitude

Answer 6 What is the distance between two adjacent wave compressions? A. 1 m/s B. 1 wavelength C. 1 Hz D. 1 amplitude