Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics: Prism: A Prism is a portion of a transparent medium bounded by two plane faces inclined to each other at suitable angle. Refraction of Light Through a Prism: Lat us consider a triangular prism ABC. Let angle of incidence and angle of refraction at first phase AB are […]
Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics: Combination of Thin Lenses in Contact: Let two lenses A and B of focal lengths f₁ and f₂ placed in contact with each other. An object is placed at a point O beyond the focus of the first lens A. The first lens produces an image at I’
Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics: Power of a Lens: The ability of a lens to converge or diverge the rays of light incident on it is called the power of the lens. The SI unit of power of lens is dioptre(D). The power of a lens is measured as the reciprocal of its
Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics: Linear Magnification Produced by a Lens(m): Linear magnification of a lens is defined as the ratio of the height of the image formed by the lens and height of the object. Here we will use hᵢ and h₀ with sign. Height above principal axis is positive and below
Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics: Lens Maker’s Formula: With the help of this formula, we can design a lens of desired focal length by adjusting R₁ and R₂. Derivation: When a Ray of light from object O incident at first surface it bends towards the normal and if we extend it, then it
Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics: Thin Lens Formula: It is a relation between focal length of a lens and distance of object and image from optical centre of the lens. Let O be the optical centre and f be the principal focus of a convex lens of focal length OF= f, Distance of
Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics: Image Formation in Lenses Using Ray Diagrams: (I) Rays which are parallel to the principal Axis after refraction, will passes through principal focus in case of convex lens and will appear to be coming from principal focus in case of concave lens. (II) Rays passing through or directed
Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics: Lens: Lens is a transparent refracting medium bounded by two surfaces, one of which must be spherical. Lenses are two types- (I) Convex or converging lens (II) Concave or diverging lens Convex Lens: A lens which is thicker at the centre and thinner at its ends is called
Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics: Refraction at a Spherical Surface: We will consider two transparent medium of refractive index n₁ and n₂, the boundary between two surfaces is a spherical surface of radius R. Assumptions: 1. All the rays are paraxial, that means P and P’ are coincide. 2. θ₁ and θ₂ are very
Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics: Total Internal Reflection(TIR): When a Ray of light strikes the interface at the angle greater than Critical Angle, it comes back in the same medium, this phenomenon is called total internal reflection(TIR). Necessary Conditions for TIR: 1. The light must travel from denser to rarer medium. 2. Angle
