Light and Telescopes

• Light rays bend as they leave the water, an effect called refraction.
• Our eyes assume light travels in straight lines, so tracing back refracted light rays does not lead to the origination point of the light.
• Light from fish in deep water makes them appear to be in shallower water.

How Light Refracts

• Light bends when it travels at an angle from one medium to another.
• Refraction happens when light changes speed.
• The speed of light in space (a vacuum) is approximately 300 000 km/s.
• Space is a vacuum, so light is not slowed down by particles.
• Light bends and refracts if it strikes a medium of different density at an angle.
• The denser the new medium, the more the light slows down, the more it refracts

Refraction Analogy

• Skaters are used as an analogy to how light refracts
• Skaters initially travel at the same speed.
• Some skaters meet a rough patch of ice and slow down.
• Those that do not meet the rough patch continue at their initial speed, causing a bend in the line.
• A beam of light bends in the same way, when part of it slows down while the rest keeps going.

Inquiry Activity: From Air to Solids

• This experiment investigates how light passes through air and transparent solids.
• Materials required: glass block, paper, pencil, ruler, protractor, ray box with a single slit, transparent plastic block.
• Procedure step 1: Place the glass block on paper, trace its outline, mark a point, draw a normal (perpendicular line).
• Procedure step 2: Direct a light ray along the normal; the entry point is the point of incidence.
• Procedure step 3: Mark the exit point, join incident and exit points to show the refracted ray.
• Procedure step 4: Shine a light ray at an angle to the normal, keeping the point of incidence the same.
• Procedure step 5: Trace the incident ray and the refracted ray coming out, ensuring you label them correctly.
• Procedure step 6: Repeat steps 4 and 5, using different angles of incidence each time.
• Procedure step 7: Use a ruler to complete each refracted ray, adding arrows to indicate direction of all rays.
• Procedure step 8: Measure the angle of incidence and refraction; create a table to organize data with the headings “angle of incidence" and "angle of refraction.”
• Procedure step 9: Repeat the experiment with the plastic block, predicting any changes in refraction.
• Analyzing and Interpreting: Questions include comparing incident and refracted angles, ray behavior upon entry along the normal, and changes with increasing incidence angle.
• Forming Conclusions: Identify factors affecting light refraction and which substance (glass or plastic) refracts more.

Refraction in Daily Life

• Mirage: An optical illusion where the road ahead on a hot day looks wet, this is caused by refraction.

Ray Diagrams

• Ray diagrams may be used to show refraction
• In the diagrams, the angle of incidence and the angle of refraction are clearly labelled

Lenses Refract and Focus Light

• Lenses are used in microscopes, telescopes, and binoculars.
• Lenses are curved pieces of glass or transparent material, shaped to refract light predictably.
• Lenses can form images by refracting light rays.

Concave Lenses

• Concave lenses are thinner in the center than at the edges.
• Parallel rays passing through a concave lens are refracted away from the lens's centre, causing light rays to diverge and light rays will never meet on the other side of the lens.

Convex Lenses

• Convex lenses curve outward and are thicker in the middle, also known as a double convex lens.
• Parallel light rays travel through a convex lens and refract toward the centre.
• Light rays move toward each other as they pass through a convex lens.
• The light rays cross at the focal point of the lens.
• The ability to converge light rays makes convex lenses useful as light collectors.
• Convex lenses are used in refracting telescopes to collects and focuses starlight.
• Convex lenses form a real image.
• The light rays meet and the image is projected onto a screen.
• Depending on the object's proximity to the lens, images can be smaller or larger.
• Convex lenses create upside-down images.

Checking Out Images - Inquiry Activity

• This experiment investigates how the distance between an object and a convex lens affects the image formed.
• Materials: Cardboard stand, paper, tape, bulb and socket, battery and wires, convex lens, modeling clay, metre-stick.
• Procedure:
• Measure the height of the lit portion of the bulb.
• Tape paper onto cardboard to act as a screen
• Determine focal length, or use the teacher's length: place the lens between the stand and lit bulb, and slowly bring screen forward, and then slowly backwards, the bulb will come into focus on the screen
• Record the bulb height and focal length.
• A data table will be used to record data on the size of the image of the bulb and the distance of the bulb from the lens.
• Place the bulb more than twice the focal length away from the lens and move the screen until the image comes into focus.
• Record the distance from the bulb, and the position of the image from the lens
• Place the bulb just over one focal length away from the lens and move the screen until the image comes into focus.
• Record the distance from the bulb, and the position of the image from the lens
• Place the bulb less than one focal length away from the lens and move the screen to attempt to focus, if focus cannot be achieved, estimate. size by looking through lens.
• Analyzing and Interpreting: The questions include: Is the image formed by a convex lens always upside down, what conditions are the the image upright, what happens to the size of the image as the bulb moves toward the lens, what happens when the bulb is placed inside the focal length of the lens?
• Forming Conclusions: How is image size and location affected by lens placement?

Applications of Convex Lenses

• Convex lenses are often used in projectors.
• Projectors may have to over come the "upside-down" problem.

Image Formation and Convex Lenses

• Image formation by a convex lens depends on the object's distance from the lens.
• With image formation and convex lenses, If the object is farther away than the focal point, the image is upside down which creates real images.
• If the object is closer than the focal point, the image is upright, bigger, and on the same side as the object (like a magnifying glass).

Lenses Switch-A-Roo Experiment

• This experiment investigates the questions: How does image formation vary when two convex lenses are used?
• Procedure:
• Make a hypothesis.
• Decide on the materials and equipment to test the hypothesis.
• Decide if there are any safety considerations.
• Plan procedure to collect needed data.
• Get procedure approved by teacher.
• Decide on data collection table look and construct.
• Before investigation, predict the size and locations of the images.
• Perform investigation and compare your results with your hypothesis, and explain results
• Compare results with classmates who investigated similar questions.
• Compare experimental procedure with classmates who investigated questions, and identify strengths and weaknesses
• Determine if more investigation can be done to further analyze.
• Outline other experiment to investigate this topic further.

Careers in Photography

• Professional photographer Ray Boudreau's portfolio includes corporate executives and members of the Royal Canadian Air Farce
• Ray Boudreau became interested in photography at age 11.
• The most challenging part of his job is that each picture has its own photographic problem
• Boudreau used a wide-angle lens from a helicopter to photograph the city of Toronto for a magazine cover.
• Ray Boudreau uses cameras fitted with different lenses, that may be a combination of convex and concave lenses.
• Wide angle lenses make make objects look farther away than they really are,
• Normal lenses make make objects look as they would to your own eye,
• Telephoto lenses make make objects look closer than they really are,

Section Review Questions

• Use a labelled diagram to illustrate the law of reflection. Make sure to indicate how rays of light would travel through the device.
• As Figure 2.35 indicates, it is possible to build a spy device with a long tube or milk carton. This could also be used to see over a crowd at a parade. Using a diagram, explain how mirrors are arranged in this device to make it an effective “spy tool.”
• Design a reading light that someone could use without bothering others in the room. (Hint: How could a mirror help?)
• If you wanted to block out all of the light from your bedroom, what type of material would you use on the window? What would you use if you wanted to block out half of the light?
• In Figure 2.36, the doll in the tank of water illustrates light from the doll reaching your eyes by three different paths. Explain what is happening to the light rays on those three paths.
• Describe how you would project a bigger image with a double convex lens.
• Why should the pages of a book be slightly rough rather than very glossy?
• Trace Figure 2.37 into your book.
• Assume the light ray moved from substance A to B. Add an arrow to the light ray, draw a normal, and label the angles of incidence and refraction.

Focus on Science

• Scientists strive to gain knowledge of the natural world.
• Why do you think it is important to learn how light reacts in nature?
• How has the development of different types and applications of lenses and mirrors helped us to better understand our world?
• How does an understanding of how light travels aid in the development of new technologies?
• Light travels at 9 460 500 000 km in one year.

Light Up Your Life Inquiry Notes

• At Station A - Blue, red, and green colored filters are shown separately over three light sources of equal brightness and shined on a white screen
• At Station A - 2 different colored lights are then overlapped to mix.
• At Station A - The combinations and results are charted.
• At Station A - All three colored lights are overlapped together on the screen and observed
• At Station B - A flat mirror is used
• At Station B - The image is observed as the subject steps back from the mirror.
• At Station C - Graph or lined paper is used to look through a convex lens and a concave lens.
• At Station C - The distances between the lines are observed when each lens is moved further away from the paper.
• At Station C - The distances between the lines are observed when each lens is moved closer to the paper.
• At Station D - A teacher turns off the lights and shines a laser through a container filled with water mixed with a little cornstarch.
• At Station D - The laser is held below the waterline at different angles. The laser and the light beam in the water are observed.
• At Station D - The laser is held above the waterline at different angles. Notice the differences.
• At Station E -A light source is shined through a glass, then tissue paper, and lastly through a book, the results are observed
• At Station F - Solar-powered devices are used to show that light is energy.
• At Station F - The amount of light that reaches the devices is changed to see how the level of power varies.

Introduction to Light

• The medical field uses tools to see inside the body without invasive surgery.
• An endoscope contains a camera, and light source.
• Light is delivered through a flexible fiber optic cable.
• Light helps doctors illuminate the digestive system and identify problems.
• Doctors use visible light, lasers, X-rays, and gamma rays to advance medical treatments.
• Lasers are used to make incisions in surgery.
• X-rays are used to view dense structures.
• Gamma rays are used to treat cancerous tissue.
• Microwaves are used to shrink enlarged tissues.

Wave Model of Light

• Models help explain characteristics and properties.
• Light and waves both have similarity, they are both a from of energy and they travel in all directions.

Properties of Waves

• All waves have amplitude, wavelength, and frequency.
• Amplitude: The height of a wave from rest to crest.
• Wavelength: The distance from crest to crest.
• Frequency: The number of times the medium vibrates in a given unit of time.
• Wavelengths vary with differing amounts of energy.
• As frequency increases, wavelengths shorten.

Tsunami

• In 1771, a tsunami that hit Japan measured 85 m high.
• The tsunami had enough energy to toss a 750-ton rock 2.5 km inland.

Math Link

• Speed can be calculated via a wave's wavelength and frequency.
• The formula is: speed = wavelength x frequency.

Light Waves

• Rainbows have fascinated people for thousands of years.
• Sunlight is always needed to create a rainbow.
• White light, when shone through a prism, refracts and splits into colored bands.
• The refracts produces the visible light spectrum.
• The visible light spectrum occurs because each colour of light is refracted at a different angle.
• White light is composed of many different colours of light.

Reasearch:

• When rainbows form sometimes a secondary rainbow appears.
• Find out what makes the secondary rainbow appear and if the order of colors is the same as the first.

The colours of the spectrum

• The colours of the spectrum can be explained using the wave model.
• Each colour has a slightly different wavelength.
• Red light has a wavelength of 700 nm.
• Violet light has a wavelength of 400 nm.
• A nanometer is one-billionth of a meter

The Invisible Spectrum

• The sun sends out lots of different types of energy we cannot see or feel, in addition to visible light.
• The sun drenches earth by energy.
• The wavelengths making up visible light explains only a small part of a larger range of electromagnetic radiation.
• Frequency increases as the wavelengths get shorter
• Low-frequency radio waves, microwaves, and infrared radiation can be found
• It is possible to find ultraviolet radiation, X-rays, and gamma rays that has shorter frequencies higher than visible light.
• Human eyes are not sensitive to either end of the electromagnetic spectrum, thus these lights are invisible.

Uses of the Electromagnetic Spectrum

Radio Waves:

• Radio waves are vital to communications.
• Different wavelengths separate modes of communication. Microwaves:
• Microwaves have a shorter wavelength, which means they have a higher frequency.
• Microwaves make water particles vibrate when heating food. Infrared Waves:
• Infrared waves are felt as heat.
• Devices can sense infrared radiation and detect hotter or cooler areas.
• Images of infrared radiation are called thermograms. Ultravoilet Light:
• Ultraviolet light is high energy and can burn the skin, increasing the risk of skin cancer. X-Rays and Gamma Rays:
• X-rays and gamma rays are high-energy radiation that can penetrate tissues.
• Lower-energy X-rays have difficulty passing through bone, making them useful for medical imaging.
• Gamma rays are used to kill cancer cells. They are administered in short bursts because long-term exposure can cause cancer.

Applications of Electromagnetic Radiation

• Electromagnetic waves are transmitted, reflected and absorbed, as is visible light.
• Radio waves can be used in medicine to produce images of tissues.
• Radio waves energize atoms and make them line up via magnetic resonance imaging (MRI).
• Then the radio waves send the different tissues and the MRI will construct a computer image.
• Radar stands for radio detection and ranging and they emit waves in order to indicate objects.
• Microwaves are sent out by radar devices in order to detect objects.

Types of Bulbs

• Incandescent bulb's electricity flows through a wire filament, and the wire will glow white-hot.
• In a fluorescent bulb, it is a glass tube is filled with a gas (mercury vapour). Electricity makes the gas in the bulb emit ultraviolet radiation.
• The ultraviolet radiation strikes a phosphor on the inside of the bulb, which then glows and emits white light.

Kinds of Light

• Phosphorescence is the way a substance emits light for a long time after radiation stops.
• Fluorsescence is the way a phosphor emits light as its being hit by light.

Source of Light

• Convenience, appearance, and durability all influence choices for artificial light sources.
• Cost of energy should be considered when choosing light bulbs.

Comparing Light Bulbs experiment

The Question: Which type of light bulb releases the most heat? Materials: 60-W incandescent, 60-W halogen, 15-W fluorescent (or varieties that give off similar amounts of light), gooseneck lamps, thermometer, beaker, water, test tube, felt marker, and timer. Do not touch bulbs during experiment, they can reach very high temperatures. Procedure: Each bulb must be placed into a lamp. Create a table to record temperature data every 30s for 5 minutes. Fill the tube with water, and put the thermometer into the test tube. Start the timer and have a partner turn on the lamp. Never hold water/liquid above a lamp socket. Gently move the thermometer up and down in the water during the trial, to ensure it heats evenly. Repeat, and replace the water in the test tube. construct the graph, using data from experiment. And write summaries. Light bulbes will generate similar light, but different heat.

Efficientcy of light bulbs

• Most light bulbs produce more heat than light.
• Incandescent produce 95% and 5% of light.
• Fluorscent produce 80% heat.

Source of Natural Light

• The most important light source is the sun.
• Light that is produced by live organism is called bioluminescence.
• Firefly has a light producing organ called photophore on the outside of its abs.
• Chemical light does not waste heat.
• Fish deep have bacteria in their photopores that performs the light chemical recation.
• A black sea dragon and the anger fish a specail long spike with a bulb of light producing bacteria.
• The spine acts a fishing rod.
• Flashlight fish use light to keep their school together and to quickly turn their photophores off fi a predator approches.