Light Waves

Question 1

Reflecting Light

Answer 1

We see objects because they produce light that travels directly into our eyes, (luminous objects , or they reflect visible light into our eyes).

Question 2

Health and Saftey

Answer 2

Experiments using lasers , never look directly at laser . The intensity of the beam can cause permanent damage to the retina.

Question 3

Images in the mirror

Answer 3

• Seeing images in mirror it it is a result of the reflection of light
• Light travels in straight lines
• if the mirror is not flat , the image is distorted .

Question 4

Mirror reflection rules + diagram

Answer 4

• The ray hitting mirror is called incident ray
• Ray bouncing off is called the incident ray
• Line drawn at 90 degrees = normal.

Question 5

Drawing the Normal

Answer 5

Question 6

Angles definition

Answer 6

Angle of Incidence - is the angle between the incident ray the normal (label it with an i)
Angle of reflection - is the angle between normal and reflected ray (label with r)

Question 7

Angle of incidence = angle of reflection

Answer 7

Question 8

REFRACTED LIGHT

Answer 8

Refraction is the bending of a wave (changing direction ) as it passes from a less to denser medium, bending towards the normal.

Question 9

Refractive index

Answer 9

• Every substance that allows light to pass through it has a refractive index , (diamonds optical properties is because of its extremely high refractive index)

Question 10

Example problem with refractive index

Answer 10

Question 11

Experiment to measure the refractive index of glass, method

Answer 11

• Place a rectangular block in the centre of a plain piece of paper and draw around it
• Mark a point in the middle of one of the long sides . This point is your target
• Remove the glass block and draw the normal passing through the target
• Measure your first angle of incidence using a protractor draw incident ray
• Using the laser , direct a beam along ray you have drawn
• replace the block
  -Mark your points , measure the incidence
• Repeat experiment

Question 12

Total internal reflection

Answer 12

This is when light travels through a more dense medium to a less dense medium eg. Air . The angle of incidence is then greater then the critical angle, then all light is reflected back into the denser medium.

Question 13

Critical angle

Answer 13

Critical angle is the Angle of incidence at which light refracts at 90 degrees when passing from a more to less dense medium

Question 14

Critical angle equation

Answer 14

Question 15

Diagrams how to draw

Answer 15

Question 16

Uses of Total Internal Reflections

Answer 16

Binoculars, to see light - have two origins , the total internal reflection in the prisms enable there to be a longer distance between light at front and eyepiece lens

Reflecting hi-ziv jackets

Optical fibres - used for internet, communication , cable television by sending pulses of light along very thin glass cables .

Endoscopes - medical devise used to take photos inside humans bodies.

Question 17

Refraction and creating spectram

Answer 17

Red longest - violet shortest

Question 18

what are light waves

Answer 18

transverse waves that can be reflected and refracted