Light Chapter Notes | Physics for GCSE/IGCSE - Year 11 PDF Download

 Page 1


Light
? It is a form of energy that enables us to see objects
? Characteristics of light
? Light is an electromagnetic wave
? Light travels in a straight line (rectilinear propagation of light)
? It can travel through vacuum
? The speed of light is 3 x 10^8 m/s
? The speed and wavelength of light changes when it travels from one medium to another
? Reflection of light
? The phenomenon of bouncing back of light in the same medium of striking the surface of any
object
? Incidence ray
? The ray of light which strikes the surface
? Reflected ray
? The ray of light that bounces back from the surface
? Normal ray
? An imaginary line (perpendicular) drawn from the point of incidence of the surface
? Angle of incidence
? The angle between the incident ray and the normal ray
? Angle of reflection
? The angle between the reflected ray and the normal ray
Page 2


Light
? It is a form of energy that enables us to see objects
? Characteristics of light
? Light is an electromagnetic wave
? Light travels in a straight line (rectilinear propagation of light)
? It can travel through vacuum
? The speed of light is 3 x 10^8 m/s
? The speed and wavelength of light changes when it travels from one medium to another
? Reflection of light
? The phenomenon of bouncing back of light in the same medium of striking the surface of any
object
? Incidence ray
? The ray of light which strikes the surface
? Reflected ray
? The ray of light that bounces back from the surface
? Normal ray
? An imaginary line (perpendicular) drawn from the point of incidence of the surface
? Angle of incidence
? The angle between the incident ray and the normal ray
? Angle of reflection
? The angle between the reflected ray and the normal ray
? Law of reflection
? The incident ray reflected ray and normal ray at the point of incidence lie on the same plane
? The angle of incidence is always equal to the angle of reflection
? Mirrors
? Plane mirrors
? Spherical mirrors
¦ Convex )(
¦ Concave ()
? Image
? A picture that is obtained on the screen
? Real image
¦ An image that can be obtained on the screen.
¦ It is inverted
? Virtual image
¦ An image that cannot be obtained on the screen
¦ It is erect or upright/the same
? Characteristics of image in plane mirror
? The image is virtual
? The image is laterally inverted (the left right reversal of an object is lateral inversion
? The size of the image is the same as the size of the object
? The object distance and mirror distance is equal
? The object is formed behind the mirror
? If angle of reflection is more than the angle of incidence, velocity decreases and vice versa
? Refractive index
? Speed of light in air/vacuum/speed of light in medium
? 3.0 x 10^8 m/s
? Sin i/Sin r (rarer/denser(
? Refractive index
? The quantity that describes how much light is slowed down
Page 3


Light
? It is a form of energy that enables us to see objects
? Characteristics of light
? Light is an electromagnetic wave
? Light travels in a straight line (rectilinear propagation of light)
? It can travel through vacuum
? The speed of light is 3 x 10^8 m/s
? The speed and wavelength of light changes when it travels from one medium to another
? Reflection of light
? The phenomenon of bouncing back of light in the same medium of striking the surface of any
object
? Incidence ray
? The ray of light which strikes the surface
? Reflected ray
? The ray of light that bounces back from the surface
? Normal ray
? An imaginary line (perpendicular) drawn from the point of incidence of the surface
? Angle of incidence
? The angle between the incident ray and the normal ray
? Angle of reflection
? The angle between the reflected ray and the normal ray
? Law of reflection
? The incident ray reflected ray and normal ray at the point of incidence lie on the same plane
? The angle of incidence is always equal to the angle of reflection
? Mirrors
? Plane mirrors
? Spherical mirrors
¦ Convex )(
¦ Concave ()
? Image
? A picture that is obtained on the screen
? Real image
¦ An image that can be obtained on the screen.
¦ It is inverted
? Virtual image
¦ An image that cannot be obtained on the screen
¦ It is erect or upright/the same
? Characteristics of image in plane mirror
? The image is virtual
? The image is laterally inverted (the left right reversal of an object is lateral inversion
? The size of the image is the same as the size of the object
? The object distance and mirror distance is equal
? The object is formed behind the mirror
? If angle of reflection is more than the angle of incidence, velocity decreases and vice versa
? Refractive index
? Speed of light in air/vacuum/speed of light in medium
? 3.0 x 10^8 m/s
? Sin i/Sin r (rarer/denser(
? Refractive index
? The quantity that describes how much light is slowed down
? Total internal reflection
? Two condition for total internal reflection must be met
? The light must be going from a more dense medium towards a less dense ore
? The angle of incidence must be greater than critical angle
? If the angle of incidence is greater than the critical angle, the light is reflected back into the same
medium. THis phenomenon of light is called total internal reflection
? Critical angle
? The critical angle is the angle of incidence where the angle of refraction is 90 degree
? The light must travel from an optically more dense medium to an optically less dense medium
? Refractive index and critical angle
? The critical angle(c) of a material is related to its refractive index (n)
? sin(c) = 1/n
? N = 1/sin(C)
? Law of refraction
? The incident ray, refracted ray and normal ray at the point of incidence lie on the same plane
? The angle of incidence is always equal to the angle of reflection
? How does total internal reflection occur
? When the light is moving from a denser medium towards a less dense one
? All the light is reflected
? Angle of incidence is greater than critical angle
? Optic fibres
? Optic fibres can be made very thin and flexible
? This can be used in medicine industry and communication
Page 4


Light
? It is a form of energy that enables us to see objects
? Characteristics of light
? Light is an electromagnetic wave
? Light travels in a straight line (rectilinear propagation of light)
? It can travel through vacuum
? The speed of light is 3 x 10^8 m/s
? The speed and wavelength of light changes when it travels from one medium to another
? Reflection of light
? The phenomenon of bouncing back of light in the same medium of striking the surface of any
object
? Incidence ray
? The ray of light which strikes the surface
? Reflected ray
? The ray of light that bounces back from the surface
? Normal ray
? An imaginary line (perpendicular) drawn from the point of incidence of the surface
? Angle of incidence
? The angle between the incident ray and the normal ray
? Angle of reflection
? The angle between the reflected ray and the normal ray
? Law of reflection
? The incident ray reflected ray and normal ray at the point of incidence lie on the same plane
? The angle of incidence is always equal to the angle of reflection
? Mirrors
? Plane mirrors
? Spherical mirrors
¦ Convex )(
¦ Concave ()
? Image
? A picture that is obtained on the screen
? Real image
¦ An image that can be obtained on the screen.
¦ It is inverted
? Virtual image
¦ An image that cannot be obtained on the screen
¦ It is erect or upright/the same
? Characteristics of image in plane mirror
? The image is virtual
? The image is laterally inverted (the left right reversal of an object is lateral inversion
? The size of the image is the same as the size of the object
? The object distance and mirror distance is equal
? The object is formed behind the mirror
? If angle of reflection is more than the angle of incidence, velocity decreases and vice versa
? Refractive index
? Speed of light in air/vacuum/speed of light in medium
? 3.0 x 10^8 m/s
? Sin i/Sin r (rarer/denser(
? Refractive index
? The quantity that describes how much light is slowed down
? Total internal reflection
? Two condition for total internal reflection must be met
? The light must be going from a more dense medium towards a less dense ore
? The angle of incidence must be greater than critical angle
? If the angle of incidence is greater than the critical angle, the light is reflected back into the same
medium. THis phenomenon of light is called total internal reflection
? Critical angle
? The critical angle is the angle of incidence where the angle of refraction is 90 degree
? The light must travel from an optically more dense medium to an optically less dense medium
? Refractive index and critical angle
? The critical angle(c) of a material is related to its refractive index (n)
? sin(c) = 1/n
? N = 1/sin(C)
? Law of refraction
? The incident ray, refracted ray and normal ray at the point of incidence lie on the same plane
? The angle of incidence is always equal to the angle of reflection
? How does total internal reflection occur
? When the light is moving from a denser medium towards a less dense one
? All the light is reflected
? Angle of incidence is greater than critical angle
? Optic fibres
? Optic fibres can be made very thin and flexible
? This can be used in medicine industry and communication
? Advantages of optic fibres
? Optic fibres consists of hair size threads of glass or plastic through which light can travel
? The inner part of the fibre is called core that carries the light and the outer concentric shell is
called cladding
? Lenses
? Lenses are made up of transparent material like glass or plastic
? Types of lenses
? Convex/ converging lens
? Concave lens/ diverging lens
? Convex lens
? If the lens is thicker in the centre than the edges, it is called convex lens
? Uses of convex lenses
? Magnifying glass
? Cameras and eyeglasses
? Telescope and Microscopes
? Concave lens
? If the lens is thinner in the centre than in the edges, it is called concave lens
? Centre of curvature
? Centre of sphere
? Principal axis
? A straight line passing through the centre of curvature of the lens
? Principle focus (convex)
? When a parallel beam of light incident on a convex lens after refraction, all the refracted rays
meet at a common point on the principal axis
? Principle focus (concave)
? Focus is virtual, after refraction, the reflected
rays are diverging away from the lens
? Optical centre
? Geometric centre of the lens
? Focal length
Page 5


Light
? It is a form of energy that enables us to see objects
? Characteristics of light
? Light is an electromagnetic wave
? Light travels in a straight line (rectilinear propagation of light)
? It can travel through vacuum
? The speed of light is 3 x 10^8 m/s
? The speed and wavelength of light changes when it travels from one medium to another
? Reflection of light
? The phenomenon of bouncing back of light in the same medium of striking the surface of any
object
? Incidence ray
? The ray of light which strikes the surface
? Reflected ray
? The ray of light that bounces back from the surface
? Normal ray
? An imaginary line (perpendicular) drawn from the point of incidence of the surface
? Angle of incidence
? The angle between the incident ray and the normal ray
? Angle of reflection
? The angle between the reflected ray and the normal ray
? Law of reflection
? The incident ray reflected ray and normal ray at the point of incidence lie on the same plane
? The angle of incidence is always equal to the angle of reflection
? Mirrors
? Plane mirrors
? Spherical mirrors
¦ Convex )(
¦ Concave ()
? Image
? A picture that is obtained on the screen
? Real image
¦ An image that can be obtained on the screen.
¦ It is inverted
? Virtual image
¦ An image that cannot be obtained on the screen
¦ It is erect or upright/the same
? Characteristics of image in plane mirror
? The image is virtual
? The image is laterally inverted (the left right reversal of an object is lateral inversion
? The size of the image is the same as the size of the object
? The object distance and mirror distance is equal
? The object is formed behind the mirror
? If angle of reflection is more than the angle of incidence, velocity decreases and vice versa
? Refractive index
? Speed of light in air/vacuum/speed of light in medium
? 3.0 x 10^8 m/s
? Sin i/Sin r (rarer/denser(
? Refractive index
? The quantity that describes how much light is slowed down
? Total internal reflection
? Two condition for total internal reflection must be met
? The light must be going from a more dense medium towards a less dense ore
? The angle of incidence must be greater than critical angle
? If the angle of incidence is greater than the critical angle, the light is reflected back into the same
medium. THis phenomenon of light is called total internal reflection
? Critical angle
? The critical angle is the angle of incidence where the angle of refraction is 90 degree
? The light must travel from an optically more dense medium to an optically less dense medium
? Refractive index and critical angle
? The critical angle(c) of a material is related to its refractive index (n)
? sin(c) = 1/n
? N = 1/sin(C)
? Law of refraction
? The incident ray, refracted ray and normal ray at the point of incidence lie on the same plane
? The angle of incidence is always equal to the angle of reflection
? How does total internal reflection occur
? When the light is moving from a denser medium towards a less dense one
? All the light is reflected
? Angle of incidence is greater than critical angle
? Optic fibres
? Optic fibres can be made very thin and flexible
? This can be used in medicine industry and communication
? Advantages of optic fibres
? Optic fibres consists of hair size threads of glass or plastic through which light can travel
? The inner part of the fibre is called core that carries the light and the outer concentric shell is
called cladding
? Lenses
? Lenses are made up of transparent material like glass or plastic
? Types of lenses
? Convex/ converging lens
? Concave lens/ diverging lens
? Convex lens
? If the lens is thicker in the centre than the edges, it is called convex lens
? Uses of convex lenses
? Magnifying glass
? Cameras and eyeglasses
? Telescope and Microscopes
? Concave lens
? If the lens is thinner in the centre than in the edges, it is called concave lens
? Centre of curvature
? Centre of sphere
? Principal axis
? A straight line passing through the centre of curvature of the lens
? Principle focus (convex)
? When a parallel beam of light incident on a convex lens after refraction, all the refracted rays
meet at a common point on the principal axis
? Principle focus (concave)
? Focus is virtual, after refraction, the reflected
rays are diverging away from the lens
? Optical centre
? Geometric centre of the lens
? Focal length
? It is the distance between the principal focus and optical centre
? Ray diagram rules
? A ray diagram is a representation of the possible paths light can take to get from one place to
another
? Rule 1 - incident light rays that are parallel to the principal axis will pass through the focal point
after refracting through the lens
? Rule 2 - Incident light rays are directed at the optical centre will pass directly through in other
words, they are not refracted
? Rule 3 - Incident rays that pass through the focal point before hitting the lens will become
parallel to the principal axis after refracting through the lens
Image formation at convex lens
? Object outside 2F ? Real, inverted, smaller, Image formed between F’ and 2F’
? Object at 2F ? same size, inverted, real, image formed at 2F’