Draw a ray diagram of refraction of light in a glass slab.

The refractive index of a material can be understood as a dimensionless number that describes how fast light travels through the material (here say, glass). It is defined as n = c v Where c is the speed of light in vacuum and v is the phase velocity of light in the medium. Through a glass slab, the light before coming back to the air suffers refraction two times. At the second time, the refracted ray bends away from the normal. If the light is incident at right angles then it will pass through the glass slab without any deviation. The ray diagram of refraction of light in a glass slab is as follows:

Draw a ray diagram for image formation by the concave mirror when the object is placed between the center of curvature ‘C’ and focus ‘F’.

When the object is placed between centre of curvature and principal focus of a concave mirror the image formed is beyond C as shown in the figure, and it is real, inverted and magnified i.e., a larger image is formed.

Draw ray diagram for image formation by concave lens when the object is placed between infinity and optical centre ‘O’.

The image formed by a concave lens when the object is kept between infinity and optical center 'O' is virtual in nature, erect and diminished, and on the same side of the lens as the object. The image formed is between focus F1 and optical center' O'.

If magnification M is positive, what will be the nature of image?

Magnification can be defined as the ratio of the size of the image to the size of the object perpendicular to the optical axis. So, if the ratio is considered positive then the image is virtual and erect. Hence, according to these sign conventions, when the magnification is positive then the image has to be erect and virtual .

Write in your words about the magnification by a lens.

Magnification of a lens is defined as the ratio of the height of an image formed to the height of a real object. It can also be given in terms of image distance and object distance. It is equal to the ratio of image distance to that of object distance. Linear or lateral or transverse magnification refers to the ratio of image length to object length measured in planes that are perpendicular to the optical axis 1 . M = ( h i / h o ) = - ( d i / d o ) , where M = magnification, h i = image height, h o = object height, and d i and d o = image and object distance.

Write the definition of Magnification in lens.

Magnification is a ratio of two identical physical quantities like the ratio of the size of the image to the size of the object. It has no unit as it is the ratio of the same quantities. It is represented by the letter m. The size of an image can be obtained if we know the size of the object and magnification. Magnification (m) = H e i g h t o f i m a g e ( h ) ' H e i g h t o f o b j e c t ( h ) = v u . For convex lens 'm' can be more than, less than or equal to one. For concave lens 'm' is less than one.