Light enables us to see the objects around us.
Our eyes sense the objects by the light reflected by them or when the object emits light.
Plants carry out photosynthesis with the help of light energy and prepare their own food .
In photocells light can be changed into electrical energy.
Light had all the characteristics of energy.
What are two types of reflection?
The two types of reflection are:
- Regular reflection.
- Irregular or diffused reflection.
What is regular reflection?
In a perfectly flat and polished surface a parallel beam of light is reflected as a parallel beam, this type of reflection is known as regular reflection. In this type of reflection images are formed in regular reflection.
What is irregular reflection?
Irregular reflection is also known as diffused reflection.
Objects having rough and unpolished surface reflect a parallel beam of light in all the directions, such type of reflection is known as irregular or diffused reflection. In this reflection images are not formed and the light get scattered.
LAWS OF REFLECTION
Angle of incidence is equal to the angle of reflection.
The incident ray, the normal drawn to the mirror at the point incidence and the reflected ray all lie on the same plane.
Reflection in a curved mirror
There are two types of curved reflecting mirror
*Concave mirror and
Concave mirror are used by dentist, in solar furnace, and in head lights of motor vehicles.
Convex mirrors are always produce diminished virtual image of an object.
Concave mirrors are used as rear view mirrors in automobiles.
Nature of concave mirror:
Pole of the mirror-Typically, the pole of the mirror is located in the centre of the mirror’s curved surface. The incident ray of light along the principal axis on the pole of the mirror retraces its path along the principal axis. It is the focal point of the reflecting surface.
Principal focus-It is the point of convergence of a parallel beam of light that is also parallel to the principal axis after reflection from the mirror. Light from a distance source, such as sun rays, is a source of parallel beam of light. It is denoted as ‘F.’
Focal length-The distance between the pole of the mirror and the point of focus of reflected parallel rays of light which are incident on the mirror is called focal length.’f’
Centre of curvature-it is the centre of the sphere of which the mirror is a part.It is denoted by the letter ‘C’
Radius of the curvature-the radius of the sphere of the the mirror is the part is called the radius of radius of curvature.It is denoted by ‘r’.Radius of curvature will be twice the focal length.Principal axis
Object distanceThe distance of the object fromteh pole of the mirror iscalled object distanceIt is denoted by ‘u’.
Image distance.-The distance between the mirror and the image is called image distance.it isdenoted by ’v’.
What is refraction?
According to the laws of refraction, the incident ray, refracted ray, and normal to the interface of two media at the point of incidence all lie on the same plane. The sine of the angle of incidence divided by the sine of the angle of refraction is a constant. Snell’s law of refraction is another name for this.
What are the laws of refraction of light?
*At the point of incidence, the incident ray, refracted ray, and normal to the interface of two media all lie on the same plane.
* the point of incidence, the incident ray, refracted ray, and normal to the interface of two media all lie on the same plane. The sine of the angle of incidence divided by the sine of the angle of refraction is a constant. Snell’s law of refraction is another name for this.
What is total interval reflection?
It is the complete reflection of a ray of light from the surrounding surfaces back into a medium such as water or glass. The phenomenon occurs when the angle of incidence exceeds a certain limiting angle known as the critical angle.
What are the conditions of total interval deflection?
1.light ray should pass from dencer medium to rarer medium.
2.the angle of incidence must be larger than the critical angle.
What are the effects of total interval reflection?
MIGRAGE: People in hot dry areas frequently observe this.Desert travellers sometimes see the image of palm trees as if there is water near the tree.Migrage-like effect can also be seen on very hot days, giving the illusion of a pool of water at the far end of the road.We can also see the illusion on the upper part of the hot plate.Light from the sun bent by the hot air near the earth.
The appearance of the water layer at short distances in a desert or on the road is caused by an optical illusion. Mirage is an example of total internal reflection caused by atmospheric refractivity.
Reflection in a curved transparent medium
LENCES: The most obvious distinction between mirrors and lenses is that mirrors reflect light rays (light bounces back), whereas lenses refracted (pass-through) light rays. A mirror will only have one focal point, which will be directly in front of the mirror. Each side of a lens has two focal points. Let’s take a closer look at the differences between mirror and lens in the table below.
Dispersion of light: have you seen rainbow? Aren’t they beautiful?
What is dispersion of light?
White light is made up of a range of seven colours.The splitting upof white light into its constituent colours is called dispersion of light.
What is spectrum?
A spectrum (plural spectra or spectrums) is a condition that is not limited to a specific set of values but can vary, without steps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colours in visible light after passing through a prism. As scientific understanding of light advanced, it came to apply to the entire electromagnetic spectrum. It thereby became a mapping of a range of magnitudes (wavelengths) to a range of qualities, which are the perceived “colors of the rainbow” and other properties which correspond to wavelengths that lie outside of the visible light spectrum