Light
Download
1 / 79

LIGHT - PowerPoint PPT Presentation


  • 114 Views
  • Uploaded on

LIGHT. Everything written in black has to go into your notebook Everything written in blue should already be in there. WHAT IS LIGHT?. Light is a form of energy that travels away from the source producing it at a speed of 3 x 10 8 m s -1.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'LIGHT' - eli


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Light

LIGHT

Everything written in black has to go into your notebook

Everything written in blue should already be in there


What is light
WHAT IS LIGHT?

  • Light is a form of energy that travels away from the source producing it at a speed of 3 x 108 m s-1


Light


Light travels in straight lines
Light Travels in Straight Lines clearly through it e.g.

Light travels in straight lines. This can be seen in the following examples

  • Laser

  • Beam of light from a searchlight

    It can also be shown using pieces of cardboard with a small hole in the middle and a length of thread


Light


Plane mirror diagram on page 1
Plane Mirror (diagram on page 1) clearly through it e.g.

Normal

Incident ray

Reflected ray

Angle ofincidence

Angle ofreflection

i

r

Plane Mirror


Laws of reflection of light
LAWS OF REFLECTION OF LIGHT clearly through it e.g.

  • 1. The incident ray, the normal and the reflected ray all lie in the same plane

  • 2. The angle of incidence is equal to the angle of reflection (i = r)



Properties of an image in a plane mirror
Properties of an image in a plane mirror clearly through it e.g.

The image is:

  • Laterally inverted

    • E.g. your right hand appears as a left hand

    • The “ambulance” sign

  • Erect

  • Virtual

  • Same size as object


Uses of plane mirrors
Uses of Plane Mirrors clearly through it e.g.

  • Make up mirror

  • The periscope


Light

Diagram page 3 clearly through it e.g.


Light



Light

Diagram on page 26 of reflection (page 26)

Plane mirror

Sheet of paper

r

i

Pins



Light


Light

Diagram (in homework copy) of reflection (written up in homework copy)

Finder pin

Plane mirror

Object pin

O

M

I


The following goes in your homework copy
The following goes in your homework copy of reflection (written up in homework copy)

  • Method

  • Set up the apparatus as in the diagram

  • Move the finder pin in and out behind the mirror until there is no parallax between the object and its image in the mirror


Light

3. Measure the distance from the object to the mirror (OM), and the distance from the mirror to the image pin (MI)

Result

OM and MI are equal

Conclusion

The image is as far behind the mirror as the object is in front of it


Spherical mirrors page 4
Spherical Mirrors (page 4) and the distance from the mirror to the image pin (MI)

CONVEX

CONCAVE



Rules for ray diagrams for concave mirror
Rules for Ray Diagrams for Concave Mirror the principal axis

  • 1. A ray travelling parallel to the principal axis is reflected through the focus

  • 2. A ray travelling through the focus is reflected parallel to the principal axis

  • 3. For a ray which strikes the pole, angle i will be equal to angle r


Top of page 5
Top of page 5 the principal axis

  • “In parallel, out through the focus”

  • “In through the focus, out parallel”


Uses of concave mirrors
Uses of concave mirrors the principal axis

  • Spotlights

  • Reflectors in car headlights

  • Shaving and make-up mirrors


Uses of convex mirrors
Uses of convex mirrors the principal axis

  • Shops (to deter shoplifters)

  • Buses

  • Dangerous bends in roads

    • They give a wide field of view


The mirror formulae
The Mirror Formulae the principal axis

u = distance from object to mirror

v = distance from image to mirror

f = focal length


Example 2
Example 2 the principal axis

  • When an object is placed 16 cm in front of a concave mirror of focal length 8 cm, an image is formed. Find the distance of the image from the mirror and say whether it is real or virtual.


Light

v = 16 cm the principal axis



Light

Magnification the principal axis

  • m =

  • m =


Example 3 hl
Example 3 (HL) the principal axis

  • An object is placed 20 cm from a concave mirror of focal length 25 cm. Find the position, magnification and nature of the image.


Light

v = 100 cm the principal axis



Light

  • m = the principal axis

  • m =

  • m = 5


Example 4 hl
Example 4 (HL) the principal axis

  • A concave mirror of focal length 10 cm forms an erect image four times the size of the object. Calculate the object distance and its nature.


Light

u = 7.5 cm the principal axis




Light

CROSS THREADS (page 30)

RAY BOX

CONCAVE MIRROR

SCREEN

Diagram page 30



Light


Light

Incident ray one optical medium to another

i

r

Refracted ray

Glass block


Page 12 under diagram
(Page 12, under diagram) one optical medium to another

  • Less dense to more dense: bends towards normal

  • More dense to less dense: bends away from normal


The laws of refraction of light
The Laws of Refraction of Light one optical medium to another

  • 1. The incident ray, the normal and the refracted ray all lie in the same plane

  • 2. where n is a constant

    • This is called Snell’s Law


Experiment to verify snell s law and determine the refractive index of glass diagram page 27
Experiment to Verify Snell’s Law and determine the refractive index of glass (diagram page 27)

Pins

Glass Block

Sheet of paper



Light

Your graph in page 28 should look like this the corresponding graph underneath

Sin i

Sin r


Real and apparent depth page 12
Real and Apparent Depth (page 12) the corresponding graph underneath

  • A swimming pool appears to be less deep than it actually is, due to refraction at the surface of the water

  • We can calculate the refractive index of a liquid by using

    n =


Critical angle
Critical angle the corresponding graph underneath

  • The critical angle is the angle of incidence in the denser medium when the angle of refraction is 90˚


Total internal reflection
Total Internal Reflection the corresponding graph underneath

  • This occurs when the angle of incidence in the denser medium exceed the critical angle

  • The ray of light is refracted away from the normal

  • As i is increased so is r

  • Eventually r = 90˚

  • At this point i has reached the ‘critical angle’

  • If i is increased beyond the critical angle, the ray does not enter the second medium

  • It is reflected back into the first medium


Light

C = critical angle


Example
Example the corresponding graph underneath

The critical angle of glass is 41.81˚

Find the refractive index of glass

  • n =

  • n = 1/0.666

  • n = 1.5


Light

n = the corresponding graph underneath


Applications of total internal reflection
Applications of Total Internal Reflection the corresponding graph underneath

  • Periscopes (using a prism)

  • Diamonds and bicycle reflectors

  • Optical fibres – in telecommunications and by doctors


Periscope diagram page 14
PERISCOPE (diagram page 14) the corresponding graph underneath


Total internal reflection in a prism
Total internal reflection in a prism the corresponding graph underneath


Total internal reflection in a prism1
Total internal reflection in a prism the corresponding graph underneath


Light

Total internal reflection in a prism the corresponding graph underneath


Light

A the corresponding graph underneath

AIR

GLASS

B

  • Remember that rays are path-reversible


Example1
Example the corresponding graph underneath

  • The refractive index of glass is 1.5

  • This value is for a ray of light travelling from air into glass

  • So = = 1.5 =

  • Or = =


Mirages
Mirages the corresponding graph underneath

  • Mirages are caused by the refraction of light in air due to temperature variations


Light

SKY the corresponding graph underneath


Lenses
LENSES the corresponding graph underneath

  • Convex lens (converging)


Light


Ray diagrams for lenses
Ray diagrams for lenses the corresponding graph underneath

  • 1. Ray incident parallel to principal axis is refracted out through focus

  • 2. Ray incident through focus is reflected out parallel to axis

  • 3. Ray incident through optic centre continues in straight line


Lens formulae
Lens formulae the corresponding graph underneath

u = distance from object to lens

v = distance from image to lens

f = focal length


Magnification
Magnification the corresponding graph underneath

  • m =

  • Or m =



Light

RAY BOX (page 29)

CROSS THREADS

CONVEX LENS

SCREEN

(Diagram page 29)


Two lenses in contact
Two Lenses in Contact (page 29)

Where F = focal length of combination

f1 and f2 are the focal lengths of the two lenses



Light

Spectrum of Visible Light constituent colours

R

O

Y

G

B

I

V

Red is deviated the least and has the longest wavelength

Violet is deviated the most and has the shortest wavelength


Uses of lenses
Uses of lenses constituent colours

  • Magnifying glass

  • Spectacles

  • Binoculars

  • Compound microscope

  • Astronomical telescope


Magnifying glass simple microscope

F constituent colours

F

Magnifying glass/Simple Microscope

  • Is simply a convex lens, with the object placed inside the focus point

  • Image is magnified, erect and virtual


Light

The Compound Microscope constituent colours

Eyepiece

Objective lens

Fo

Fe


The compound microscope
The compound microscope constituent colours

  • Consists of 2 convex lenses

  • The first image is formed at the focal point of the eyepiece

  • The final image is formed at infinity so we view it with a relaxed eye

  • This is called ‘normal adjustment’

  • The image formed is inverted


Light

The Astronomical Telescope constituent colours

Objective lens

Eyepiece

Fe

Fo