Optics and light Waves (Grade 11)

Wishlist Share
Share Course
Page Link
Share On Social Media

About Course

Etymologically, the word optics comes from the ancient Greek word ὀπτική (OPTICKS), meaning appearance or look. Optics is the branch of physics which involves the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviolet, and infrared light.

Optics and Light
Optics and Light. Crédits : Getty Images/iStockphoto

Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties. This chapter will explore the source of light, its behaviour as a type of transverse wave and its use in different optical instruments. The other components of electromagnetic spectrum which light is a part of, will also be looked at, in terms of their origin, uses and for some, even their dangers.

Learning (Optics) Objectives

At the end of this chapter, you should be able to:

  • Describe the rectilinear propagation of light.
  • Investigate the formation of shadows and eclipse.
  • Describe reflection of light.
  • Investigate the laws of reflection of light
  • Demonstrate the formation of images by plane mirrors.
  • Identify the position of an image using plane mirrors.
  • Describe what refraction of light is
  • Explain the terms of refraction of light
  • Verify the laws of refraction of light.
  • Describe what refractive index is.
  • Investigate the refractive index of a glass block.
  • Calculate refractive index of a substance (n) using real and apparent depth.
  • Explain the term ‘critical angle’.
  • Describe the relationship between critical angle and refractive index.
  • Explain how total internal reflection occurs.
  • Explain how total internal reflection is used.
  • Describe different types of lenses.
  • Explain the action of lenses on beams of light.
  • Demonstrate how to determine the focal length,
  • Calculate the power of the converging lens
  • Demonstrate how to obtain images formed by converging lenses
  • Describe the uses of lenses in everyday life.
  • Describe main components of electromagnetic spectrum.
  • Describe the properties of electromagnetic waves
  • Identify the sources of each of the rays in the electromagnetic spectrum.
  • Describe the method of detection each of the main component of the electromagnetic spectrum.
  • Explain the use of each of the waves in the electromagnetic radiation spectrum.
  • Explain the harmful effects of ultra violet radiation, gamma rays and x-rays to life.

What You will cover in Optics

In this course, you will learn the meaning of light, and its propagation in a straight line. The difference between luminous and non-luminous objects and the role of light in our sight will be explored. The obstacles to our sight, including the formation of shadows and eclipses will also be discussed.

You will further comprehend that when rays from luminous objects strike surfaces of non-luminous objects, they bounce off the non-luminous object and enter your eye. The result is you seeing the object. This bouncing of light off objects is known as “reflection”

Although light travels in straight lines in one transparent material, such as air, if it passes into a different material, such as water, it changes direction at the boundary between the two, i.e. it is bent. This bending of light when it passes from one medium to another is called ‘refraction’.

Show More

What Will You Learn?

  • Describe the rectilinear propagation of light.
  • Investigate the formation of shadows and eclipse.
  • Describe reflection of light.
  • Investigate the laws of reflection of light
  • Demonstrate the formation of images by plane mirrors.
  • Identify the position of an image using plane mirrors.
  • Describe what refraction of light is
  • Explain the terms of refraction of light
  • Verify the laws of refraction of light.
  • Describe what refractive index is.
  • Investigate the refractive index of a glass block.
  • Calculate refractive index of a substance (n) using real and apparent depth.
  • Explain the term ‘critical angle’.
  • Describe the relationship between critical angle and refractive index.
  • Explain how total internal reflection occurs.
  • Explain how total internal reflection is used.
  • Describe different types of lenses.
  • Explain the action of lenses on beams of light.
  • Demonstrate how to determine the focal length,
  • Calculate the power of the converging lens
  • Demonstrate how to obtain images formed by converging lenses
  • Describe the uses of lenses in everyday life.
  • Describe main components of electromagnetic spectrum.
  • Describe the properties of electromagnetic waves
  • Identify the sources of each of the rays in the electromagnetic spectrum.
  • Describe the method of detection each of the main component of the electromagnetic spectrum.
  • Explain the use of each of the waves in the electromagnetic radiation spectrum.
  • Explain the harmful effects of ultra violet radiation, gamma rays and x-rays to life.

Course Content

PROPERTIES OF LIGHT
o Light is a form of energy. It may be considered as travelling in a straight line within a uniform medium, at a speed of 300 000km/s. o Visible light is the form of energy that can be detected unaided by our naked eyes. An object can only be seen if visible light coming from the object enters our eyes. o Some objects can produce light and are called luminous bodies while others cannot produce light and are called non-luminous bodies. o A group of right rays is called “a beam of light”. o The pinhole camera is used to demonstrate that light from illuminated objects travels in straight lines. o Some bodies such as moon reflect light and direct it to places where light from the source cannot reach (shadow). o Some objects can stop light completely and are called opaque whereas others just let a part of light through them and are called translucent objects o Shadows are formed when light rays strike an opaque object. a partial shadow (penumbra) forms around the total shadow, umbra. o The light rays coming from the sun cause a number of natural phenomenon which are the results of shadows. Some examples of such phenomena are night and day, the phases of the moon and eclipse. o An eclipse of the sun, also known as a solar eclipse happens when the moon comes between the sun and the earth. o An eclipse of the moon, also known as the “lunar eclipse”, occurs when the earth comes between the sun and the moon.

  • Concept of light
    00:00
  • REFLECTION OF LIGHT
    00:00
  • REFRACTION OF LIGHT
    00:00
  • DISPERSION OF LIGHT
    00:00
  • LENSES
    00:00

ELECTROMAGNETIC SPECTRUM
The Sun is the main supplier of basic energy required for all live as well as non- live processes on Earth. The transference of energy from the Sun to the Earth is carried out by electromagnetic waves. When an electric field and a magnetic field oscillate in two planes perpendicular to each other, an electromagnetic wave is produced in a direction perpendicular to both these planes. While electromagnetic waves are produced by natural phenomena they are also produced technically according to human needs. Electromagnetic waves are most prominently used in radio and TV transmissions. The X-rays used in medical examinations and in industrial activities also belong to the category of electromagnetic waves. The micro waves used in ovens for cooking purposes is another example of electromagnetic waves. The infrared rays used in the cameras of the Pathfinder rower sent by NASA for investigations on Mars are also electromagnetic waves. Ultraviolet rays, another component of electromagnetic spectrum, are harmful for living beings. Although the ozone layer above in the atmosphere has minimised the passage of these rays to Earth from the Sun naturally, the damages caused to this layer by human activities has allowed these harmful rays to penetrate through the ozone layers to reach Earth. Thus we should develop an awareness to identify these activities and to control them. Light, an essential component in our livelihood, though considered as rays in rectilinear motion for convenient study purposes is really an electromagnetic type of wave. Although it is sufficient to consider light as a form of rays in our day-to-day life, it is essential to consider the wave nature of light in advanced scientific studies. All electromagnetic waves can be arranged in a series in the descending order of their frequencies and this series is known as the electromagnetic spectrum. All electromagnetic waves travel in free space with the velocity of light, which is 3x 108 m s1, while it travels in other media with different velocities. The colourful visual representation of the electromagnetic spectrum as a function of the frequency and wavelength also showing the use of each type of EM radiation, will assist learners to connect physical concepts to real life experiences. The penetrating ability of the different kinds of EM radiation, the dangers of gamma rays, X-rays and the damaging effect of ultra-violet radiation on skin and radiation from cellphones are discussed.

Student Ratings & Reviews

No Review Yet
No Review Yet