Light The Facts of Light – Notes Light Intro Shadows.

Slides:



Advertisements
Similar presentations
What is Visible light A. EM radiation that has. a wavelength range
Advertisements

Suppose that you hold the transparency in the photograph below in front of a mirror. How will its reflection appear? Is the image: (1) inverted top-to-bottom?
Journal Writing Activity
Light Chapter 19.
Jeopardy Science Unit 2. LightReflectColorSoundWaves
By Kristine. An optical device is any technology that uses light. An optical device can be as simple as a mirror, or as complex as the Hubble Space Telescope.
Grab Bag Wave Vocabulary Mirrors Light, Mirror, and Lens Lenses
DEMONSTRATE UNDERSTANDING OF WAVES AS 2.3 LIGHT 4 WEEKS WAVES 4 WEEKS.
Light, Reflection, and Refraction Chapters 14 and 15 OPTICS.
Light. All light is produced by excited atoms Excited Atoms Electrons in an energy level have a specific amount of energy If an electron absorbs energy,
What is it? How does it work? How do we use it?. o Electromagnetic Waves display wave behavior o Created by.
Ray Diagrams Notes.
Physics Announcements
Reflection and Refraction Light interacts with matter Interaction begins at surface and depends on –Smoothness of surface –Nature of the material –Angle.
Geometric Optics Conceptual MC Questions. If the image distance is positive, the image formed is a (A) real image. (B) virtual image.
21/04/2017 KS3 Light.
Optics.
Geometric Optics September 14, Areas of Optics Geometric Optics Light as a ray. Physical Optics Light as a wave. Quantum Optics Light as a particle.
Light So far when we have talked about waves we have talked about sound waves. Light is a special type of wave.
Mirrors & Reflection.
LIGHT CH. 18. What is Light? Light is an electromagnetic wave that travels through space requiring no medium.
State Assessment Review Physical Science S.HS.2B.3.2.
Optics 2: REFRACTION & LENSES. REFRACTION Refraction: is the bending of waves because of the change of speed of a wave when it passes from one medium.
LIGHT.
Slide 1 The Physics of Light Why and how do we see light? Slide 1 The Physics of Light Why and how do we see light?
Ch23 Geometric Optics Reflection & Refraction of Light.
Ch 23 1 Chapter 23 Light: Geometric Optics © 2006, B.J. Lieb Some figures electronically reproduced by permission of Pearson Education, Inc., Upper Saddle.
 When light strikes the surface of an object  Some light is reflected  The rest is absorbed (and transferred into thermal energy)  Shiny objects,
TYPE OF IMAGE Real vs Virtual –Real Images can be seen on a piece of paper or screen placed because the focal point is in front of the mirror or behind.
Electromagnetic Waves
Refraction and Lenses.
Light, Reflection, and Refraction OPTICS. Electromagnetic Waves Magnetic field wave perpendicular to an electric field wave All objects emit EMWs. – 
Light, Reflection, and Refraction Chapters 14 and 15.
Waves- Vocabulary Wave- disturbance that transfers energy from place to place. Medium- material through which the wave travels. Vibration (oscillation)-
ResourcesChapter menu Bellringer What do you think light is? Is light made of matter? Can light travel through space? Explain your answers in your lab.
Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Waves and Particles The two most commonly used models describe light.
Behavior of Light. Getting the Idea Light is another form of energy. You can see all the objects around you because the sun (or a lamp) is sending out.
Light, optics and colour
 Mirrors that are formed from a section of a sphere.  Convex: The reflection takes place on the outer surface of the spherical shape  Concave: The.
Light refraction Chapter 29 in textbook.
It’s amazing!…Can you imagine life without it?
Sound and Light Chapter 4: Light Section 1: Light and Color 3: / 52 = 68.67% 5: / 52 = 82.08% 6: 42.44/52 = 81.62%
Chapter 13 Properties of Light: Reflection and Mirrors Herriman High Honors Physics.
THIS IS With Host... Your EMLensesMirrorsLightReflectionLight Clues.
We need light to see objects Light is energy (electromagnetic). ts/science_what_is_light.htm.
* Light is the range of frequencies of electromagnetic waves that stimulate the retina of the eye. Light waves have wavelengths from about 400 nm (4.0.
Mav Mark What are forms of the electromagnetic spectrum?
Light and Pinhole Cameras GHB 2005 Pinhole cameras are important because they demonstrate that light travels in straight lines.
Refraction and Lenses. Refraction is the bending of light as it moves from one medium to a medium with a different optical density. This bending occurs.
Reflection and Refraction of Light From “College Physics” Serway and Faughn with modifications.
Lights, Mirrors, and Lenses Light is another type of wave that carries energy. A light ray is a narrow beam of light that travels in a straight line. Light.
Chapter 19 Light, Mirrors, and Lenses Section 1 Properties of Light Pages
Click on the objects to find out and learn about light.
Light and Optics Part Three: Optics and Reflection.
Light. Light is a electromagnetic radiation - a form of energy. Light travels in a straight line. The direction in which light is travelling is known.
Reflection of Light Reflection – The bouncing back of a particle or wave that strikes the boundary between two media. Law of Reflection – The angle of.
Light Vocabulary 6 th Grade Science. Optics The study of visible light and the ways in which visible light interacts with the eye to produce vision.
Unit 3 Lesson 3 Mirrors and Lenses
LIGHT LIGHT AND COLOR.
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.
While you are watching the video think about why this is happening.
What is the nature of light?
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.
Chapter Menu Lesson 1: What is light? Lesson 2: Light and Matter
Jeopardy This is Science - Light JEOPARDY!!!
Reflection from mirrors
What is the nature of light?
Unit 3 Lesson 3 Mirrors and Lenses
Presentation transcript:

Light The Facts of Light – Notes Light Intro

Shadows

Shadow A book of height 20 cm is held 50 cm from the light and the wall is at a distance of 125 cm to the light. Find the size of the shadow. d s =

What is Light? ELECTROMAGNETIC WAVES. Electromagnetic Waves Copywrited by Holt, Rinehart, & Winston

Light is Produced when: An electric charge is accelerated Molecules, atoms or atomic nuclei make transitions to lower energy states. Cutnell & Johnson, Wiley Publishing, Physics 5 th Ed.

Electromagnetic Spectrum What are other types of electromagnetic waves? Cutnell & Johnson, Wiley Publishing, Physics 5 th Ed. Spectrum

Speed of Light Light travels at 3.00 x 10 8 m/s in a vacuum. Call this “c” – for constant speed. What can cause the speed of light to change? Passing through a transparent (clear) medium.

ROY G. BIV EM Spectruml ( m) Visible Light nm Red674 nm Orange616 nm Yellow580 nm Green556 nm Blue458 nm Indigo410 nm Violet400 nm nanometer (nm) = 1.0 x m Cutnell & Johnson, Wiley Publishing, Physics 5 th Ed.

Transparent Transparent materials transmit light – allowing it to pass through undistorted. Notice that glass blocks both infrared and ultraviolet light, but is transparent to all the frequencies of visible light!

Visible Light Translucent materials transmit light – but distort it, which means objects can’t be seen clearly. Opaque materials do not transmit light. They either reflect or absorb the light. Light & Materials

Principle of Least Time Light travels in straight lines. Among all possible paths for light to go from one point to another, light will take the path that requires the shortest time. This idea is the basis for Laws of Reflection

Light Behavior What happens when light strikes a new surface (medium)? 1. Bounce off of the new medium - REFLECTION 2. Go through the new medium and bend as it changes speed - REFRACTION 3.Be ABSORBED and changed into heat

Light bounces off Homer Light enters the eye of an observer Light is produced by a luminous object How Can We See Homer?

If light bounces off Homer in only one direction… …Homer can only be seen from one direction This observer can see Homer This observer receives no light from Homer so cannot see him Why Can We See Homer in All Directions?

When light hits a rough surface, it is scattered in many directions, so… … objects can be seen from many directions. Light Scattering

Sealed box with non-reflective coating inside (preferably black) Very small hole (pin hole!) Translucent screen (e.g. tracing paper) When the camera is pointed towards a bright object, an image of the object appears on the screen What is a Pinhole Camera?

How does a pinhole camera work? Every point on Homer’s head will scatter light in many directions, however… … only one ray of light from each point on Homer’s head is travelling in precisely the right direction to pass through the pinhole

Also… … only one ray from each point on Homer’s foot will be travelling in precisely the right direction to enter the pinhole Light is scattered as it passes through the translucent screen, so… Pinhole Camera

Image is inverted … we see an image on the screen Light scattered by screen Object Pinhole Camera

Ray diagrams show the path of rays of light from an object. They can be tricky to draw, so the best thing is to… CHEAT!!! Drawing Ray Diagrams for Pinhole Cameras

… so that the rays cross in the pinhole Step 1: Draw your object Step 3: Draw in rays from top and bottom of your object Step 4: Draw in rest of pinhole camera … Step 2: Draw your inverted image and your translucent screen Pinhole Camera

4. Light always reflects off an object at the same point that it hits the object. 5. When using a diagram to explain how somebody sees something – show the ray of light entering the eye 2. Always use an arrow head to show which direction the rays of light are travelling in 1. Always use a ruler – light travels in straight lines 3. Rays of light should touch the objects that they are reflecting off. Rules for Drawing Ray Diagrams

Pinhole Camera

Similar Triangles

Pinhole Camera Using your pinhole camera, measure the height of an apartment building that is 320 m away.

Ray An arrow drawn on a diagram to show the direction of propagation of a set of waves A ray is always at 90° to the wavefront. wavefront ray

Refraction Change in direction of a wave When waves travel across a boundary between two different media (substances), their speed changes. The change in speed can result in a change in direction of propagation of the waves. Refraction

Skateboarding on Grass Think about a skateboard example: If a skateboard is rolling from pavement to this triangular plot of grass, show its path both into and out of the grass. If the grass plot were a piece of glass, and the skateboard path were a ray of light, the light would bend the same way due to refraction. Notice that the light bends toward the base of the triangle.

Ray Tracing Show how a ray of light will bend as it passes through each piece of glass below : (To simplify, the incident ray is drawn straight to the center of the glass. Bend the ray at that point and draw a straight line out of the glass.)

Lens If a piece of glass has just the right shape, it can bend parallel light rays so that they all cross – or appear to have crossed – at a single point – focal point Such a piece of glass is called a lens.

Lens A lens is simply a combination of pieces of glass. The combination at the left is thicker in the middle and converges the light (convex lens). The arrangement at the right is thinner in the middle than at the edges; it diverges light (concave lens).

Convex Lens Convex lens – is a converging lens as it bends the light inward to a real focal point (F). –focal point can be seen –true if lens is properly shaped Copywrited by Holt, Rinehart, & Winston

Concave Lens Concave lens – is a diverging lens as it spreads the light outward away from a virtual focal point (F’). –Focal point cannot be seen, but can be found by projecting the rays back toward the light source (use dashed lines) Copywrited by Holt, Rinehart, & Winston

Focal Length The focal length (f) is the distance from the center of the lens to the focal point (F). –measured to real focal point then the focal length is positive –measured to virtual focal point then the focal length is negative

Lens Power The greater the curvature of the lens the greater the power of the lens – more refraction or bending of light. Greater the power, the shorter the focal length.

Reflection occurs when the new medium is too different from the original medium for the light ray to pass through is the process of returning re- emitted light into the medium from which it came.

1st Law of Reflection: the angle of incidence is equal to the angle of reflection. Both of these angles are measured from a normal (which means perpendicular) to the surface at the point of incidence.