What is optics?
It is the science of light
What is Geometrical Optics?
This help us to understand the basics of light, reflection and refraction and the use of simple optical elements such as mirrors, prisms, lenses
What is Geometrical Optics also know as?
Also known as Ray Optics
What is Physical Optics?
This help us to understand the phenomena of light wave, interference, diffraction, and polarization; the use of thin film coatings on mirrors to enhance or suppress reflection
What is Physical Optics also know as?
Also known as wave optics
Light sources you will talk about 2 different light source
C an be natural source such as Sun light or artificial such as heating a solid body until it glows
Point source- light source which is very small (like a laser)
Extended source- consists of several point sources or those of appreciable size (like a lightbulb)
First Law of Geometrical optics is the rectilinear propagation of light
Light rays propagating through a homogeneous transparent medium do so in straight-lines.
Best way is to illustrate with three opaque screens with pinholes, if you move even one of the screen, you will not be able to see the light source.
What 2 types of waves is Visible light in-between?
Infared and Ultraviolet
at a rage of 700-400 of visible light
What was the main debate about the nature of light in the 17th century?
The main debate in the 17th century was whether light is made up of particles or waves. Isaac Newton argued that light consisted of tiny particles, while Christian Huygens believed light was made of waves that vibrate perpendicular to their direction of travel, leading to the development of Huygens’ Principle to describe wave propagation.
Huygens principle
Any space through which light travels is called an optical medium.
Optical media with the same properties in all directions are called isotropic.
If the medium’s properties are uniform throughout, it is homogeneous.
When light originates from a point source (B) in an isotropic, homogeneous medium, it spreads out evenly at the same speed in all directions.
At any given moment, the light forms a sphere (C) with the source at its centre.
These imaginary spherical surfaces representing the positions of the light waves are called wave fronts.
What is an optical medium and how is it described when it has the same properties in all directions?
An optical medium is any space through which light travels. If it has the same properties in all directions, it is described as isotropic.
What happens when light starts from a point source in an isotropic, homogeneous medium?
Light spreads out evenly in all directions at the same speed, forming a sphere with the source at its centre.
What are wave fronts according to Huygens’ Principle?
Wave fronts are imaginary spherical surfaces that represent the positions of light waves at any given moment as they spread out from the source.
What is wavelength (λ), and how is it measured for light?
Wavelength (λ) is the distance between successive points of similar phase in a wave. For light, it is measured in nanometres (nm).
What is frequency (ν), and how is it measured?
Frequency (ν) is the number of complete waves produced in one second. It is measured in cycles per second, also known as hertz (Hz).
What is amplitude (A) in a wave?
Amplitude (A) is the peak value of a wave, representing the height of the wave crest or the depth of the wave trough. It indicates the wave’s intensity or strength.
What is velocity (v) in relation to a wave, and how is it measured?
Velocity (v) is the rate at which a wave travels, measured in metres per second (m s⁻¹). The velocity of light in a vacuum is 3 × 10⁸ m s⁻¹, which is constant for all colours of light.
What is the formula that relates velocity, frequency, and wavelength?
The velocity of light is given by the formula v = ν λ, where v is velocity, ν is frequency, and λ is wavelength.
What is a light ray, and does it physically exist?
A light ray is the path along which light travels, usually in a straight line in a homogeneous medium. It does not physically exist as a material object but is a useful concept for calculations and understanding light behavior.
What’s a group of light rays called?
A group of light rays is called ‘a pencil of rays’
What is the central ray called of each pencil called?
The central ray in each pencil is called the chief ray
What can light rays be interns of coming together?
A pencil of rays can be
divergent
convergent
parallel
How is vergence at a point in a pencil of rays defined?
The vergence at a point is the reciprocal of the distance from that point to the source or focus of the rays. For example, if the distance from point A to the source is a, then the vergence at A is 1/a
What is a sign convention in optics and why is it used?
A sign convention is a set of definite rules used to assign positive or negative signs to distances measured on an optical diagram. It helps to distinguish between diverging and converging rays, ensuring consistency in optical calculations.
