Light, Reflection & Refraction - Practice Flashcards (20)

20 Q&A flashcards covering light basics, reflection, and refraction concepts from the notes.

What is light?

A form of energy that enables us to see; it travels in straight lines, can form shadows, and has the maximum speed in this world (about 3×10^8 m/s).

What are the Laws of Reflection?

Angle of incidence equals angle of reflection; incident ray, the normal at the point of incidence, and the reflected ray lie in the same plane.

What is a Real image?

An inverted image formed by a convex lens or a concave mirror; formed on a screen due to actual intersection of rays.

What is a Virtual image?

An erect image formed by plane mirrors, convex mirrors, or concave lenses; not formed on a screen; formed by apparent (imaginary) intersection of rays.

Properties of a Plane Mirror

Object and image are at equal distances from the mirror; image is virtual if the object is real (and vice versa); size of image equals size of object; lateral inversion.

Radius of Curvature (R)

Distance between the Pole and the Centre of Curvature.

Centre of Curvature (C)

Centre of the imaginary sphere of which the mirror is a part.

Pole (P) of a spherical mirror

Mid-point of the reflecting surface.

Focus (F) for mirrors

Point on the principal axis where parallel rays converge after reflection (concave) or appear to diverge from (convex).

Aperture (in mirrors)

The effective diameter of the reflecting surface.

Focal Length (f) for a spherical mirror

Distance between the Pole and the Focus.

Principal Axis

Line joining the Pole and Centre of Curvature.

Optical Centre (for lenses)

Central point of a lens.

Ray Diagram Rule 1 (mirror)

A ray parallel to the principal axis passes through the focal point after reflection.

Ray Diagram Rule 2 (mirror)

A ray passing through the focal point emerges parallel to the principal axis after reflection.

Ray Diagram Rule 3 (mirror)

A ray passing through the centre of curvature is reflected back along the same path.

Angle relation in ray diagrams

The incident and the reflected rays make equal angles with the principal axis.

Sign Convention for object distance (mirrors)

Object distance u is measured from the pole; u is negative when the object is on the left; Focal lengths are negative for concave mirrors and positive for convex mirrors.

Lens Formula

1/f = 1/v − 1/u (where f is focal length, v image distance, u object distance).

Power of a Lens

P = 1/f (in dioptres); + for convex lenses, − for concave lenses; total power Ptotal = P1 + P2 + …