class 10 science chapter 10 in notes in hindi
Answers
Answer:
i dont know to write hindi so i gave in english
Explanation:
A medium that is polished well without any irregularities on its surface will cause regular reflection of light. For example, a plane mirror. But even then some light gets absorbed by the surface.
Laws of Reflection
The incident ray, reflected ray and the normal all lie in the same plane. Angle of incidence = Angle of reflection
[∠i=∠r]
Fermat’s Theorem
The principle of least time: Light always takes the quickest path between any two points (which may not be the shortest path).
Rectilinear propagation of light and the law of reflection [∠i=∠r] can be validated by Fermat’s principle of least time.
Plane mirror
Any flat and polished surface that has almost no irregularities on its surface that reflect light is called as a plane mirror.
Characteristics of images
Images can be real or virtual, erect or inverted, magnified or diminished. A real image is formed by the actual convergence of light rays. A virtual image is the apparent convergence of diverging light rays.
If an image formed is upside down then it is called inverted or else it is an erect image. If the image formed is bigger than the object, then it is called magnified. If the image formed is smaller than the object, then it is diminished.
Image formation by a plane mirror
The image formed by a plane mirror is always virtual and erect.
Object and image are equidistant from the mirror.
CBSE Notes Class 10 Science Chapter 10-4
To know more about Plane mirror, visit here.
Principle of Reversibility of light
If the direction of a ray of light is reversed due to reflection off a surface, then it will retrace its path.
Spherical Mirrors
Spherical mirror
Consider a hollow sphere with a very smooth and polished inside surface and an outer surface with a coating of mercury so that no light can come out. Then if we cut a thin slice out of the shell, we get a curved mirror, which is called a spherical mirror.
Relationship between focus and radius of curvature
Focal length is half the distance between pole and radius of curvature.
F = R/2
Curved Mirror
A mirror (or any polished, reflective surface) with a curvature is known as a curved mirror.
Important terms related to spherical mirror
Pole (P): The midpoint of a spherical mirror.
Centre of curvature (C): The centre of the sphere that the spherical mirror was a part of.
The radius of curvature (r): The distance between the centre of curvature and the spherical mirror. This radius will intersect the mirror at the pole (P).
Principal Axis: The line passing through the pole and the centre of curvature is the main or principal axis.
Concave Mirror: A spherical mirror with the reflecting surface that bulges inwards.
Convex Mirror: A spherical mirror with the reflecting surface that bulges outwards.
Focus (F): Take a concave mirror. All rays parallel to the principal axis converge at a point between the pole and the centre of curvature. This point is called as the focal point or focus.
Focal length: Distance between pole and focus.
Rules of ray diagram for representation of images formed
A ray passing through the centre of curvature hits the concave spherical mirror and retraces its path.
Rays parallel to the principal axis passes through the focal point or focus.
Image formation by spherical mirrors
For objects at various positions, the image formed can be found using the ray diagrams for the special two rays. The following table is for a concave mirror.
Uses of spherical mirror based on the image formed
Concave and Convex mirrors are used in many daily purposes.
Example: Rear view mirrors in vehicles, lamps, solar cookers.
Mirror Formula and Magnification
Sign convention for ray diagram
Distances measured towards positive x and y axes (coordinate system) are positive and towards negative x and y-axes are negative. Keep in mind the origin is the pole(P). Usually, the height of the object is taken as positive as it is above the principal axis and height of the image is taken as negative as it is below the principal axis.
Mirror formula and Magnification
1/v + 1/u = 1/f where ‘u’ is object distance, ‘v’ is the image distance and ‘f’ is the focal length of spherical mirror, which is found by similarity of triangles.
The magnification produced by a spherical mirror is the ratio of the height of the image to the height of the object. It is usually represented as ‘m’.
To know more about Mirror Formula, visit here.
Position and Size of image formed
Size of image can be found using the magnification formula m = h’/h = – (v/u) If m is -ve it is a real image and if it is +ve it is a virtual image.