Railway Science (Physics-Light and Optics)

-2 . Magnification: Ratio between the image height and object height. A magnification of 2 indicates the image is twice the size of the object. If the magnification is positive, then the image is upright compared to the object (virtual image). If magnification is negative then the image is inverted as compared to the object (real image). A convex lens is a lens that is thick at the middle and thin at the edges. It is used in eyeglasses for correcting farsightedness.

R/2 . The surface of a curved 𝑅 2 mirror may be either convex or concave. The distance from the pole to the focal point is called the focal length (f). The focal length of a spherical mirror is then approximately half its radius of curvature (R). Radius of curvatur = 2f.

virtual, erect and diminished. Magnification is a measure of the size of an image compared to the size of the object. Lenses and curved mirrors can produce magnified images. When the magnification is less than one, it signifies that the image formed by the lens is smaller than the original size of the object. The positive sign of magnification indicates that the image is virtual and erect.

concave, plane, convex. If the image of the child's head is bigger in the mirror because the concave mirror enlarges the image of an object. His middle portion of body is the same as a plane mirror forms the same size of image. his legs look smaller in the mirror as convex mirrors make the image smaller in size.

deviation angle. The angle of deviation is angle between the incident ray and the emerging ray. In the figure, PQR is a prism with base QR. AB is incident ray on surface PQ . It makes ∠ABN with the normal NB. This angle is angle of incidence. After entering the prism, the light ray bends towards normal. BC is refracted ray, ∠N′BC is angle of refraction. Once the refracted ray emerges from the prism into air, it bends away from normal. CD is emergent ray, ∠DCM is angle of emergence, Therefore ∠EOD is angle of deviation. Angle of incidence - angle between the normal and the ray of light. Angle of refraction - the angle between a refracted ray and the normal drawn at the point of incidence to the interface at which refraction occurs.

Violet. A refractive index is a property of the material through which the ray is passing through. The refractive index changes inversely with the wavelength. The colours in the order of the increasing wavelength are violet, indigo, blue, green, yellow, orange, and red. The violet ray has the shortest wavelength. So, it has the highest refractive ind

0°. Third rule of image formation by a convex mirror - When a ray of light going towards the focus becomes parallel to the principal axis after reflection on the mirror. This is just the reverse case of the first rule (A ray of light which is parallel to the principal axis of a convex mirror, appears to be coming from its focus after getting reflected from the mirror).

(i), (ii) and (iii). When the light ray enters the glass slab, the light ray bends towards the normal as the glass is denser than air. Therefore, angle of incidence is greater than angle of refraction. As the ray emerges out of the glass slab, it bends away from the normal. The angle of emergence is equal to the angle of incidence. As the light ray undergoes refraction two times in opposite directions, the emergent ray is parallel to the incident ray

Beyond 2F. Other Positions of Convex Lens: Placement of Object (Image Obtained) - At infinity (At F₂ , real, Inverted and highly diminished ). Object at 2F (At 2F₂ , real, inverted and Same size). Object between Focus and 2F (Beyond 2F₂ , real, inverted and magnified), Object at Focus (At infinity, real, inverted and magnified). Object is between Centre and Focus (Behind the lens, Virtual, erect and magnified).