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Edulabz InternationalCBSEPracticalSkills.com


PHYSICS PRACTICAL (CBSE) - X

Scientific Terminology / Definitions

Absolute refractive index (m) : It is the refractive index of the medium with respect toair or vacuum.

Amplitude (A) : It is the maximum displacement of the particles of the medium fromtheir original undisturbed position. It is measured in cm/m.

Angle of incidence : It is the angle between the incident ray and the normal.

Angle of reflection (r) : It is the angle between the reflected ray and the normal.

Angle of refraction (r) : The angle between the refracted ray and the normal.

Angle of emergence (e) : The angle which emergent ray makes with the normal at thepoint of emergence.

Incidentray

Reflected ray

Reflecting surface

i r

0

Angle of Incidence Angle of Reflection

Normal

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Buoyancy/upthrust : It is the upward force experienced by the immersed body when

partly or wholly immersed in a fluid. It is measured in newton.

Crests : It is the elevation in a transverse wave.

Compressions (C) : The part of a longitudinal wave where the particles of the medium

are closer to one another.

Coulomb (C) : It is the S.I. unit of charge. One coulomb is that quantity of electricity

which flows through any cross-section of a conductor in one second.

Conductors : Materials through which electric current can flow.

e.g. Copper, Silver, Aluminium etc.

Centre of curvature (C) : It is the centre of the sphere of which the mirror or lens is

a part.

Denser medium : A medium in which the speed of light is less or whose density

is more. e.g. Glass is denser than water, water is denser than air

Echo : It is the repetition of sound caused by the reflection of sound waves.

Electromagnetic waves : The waves which do not require any material medium for

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Lateral Displacement (D) : The shift in the path of light on emergence from a mediumwith parallel faces. Lateral displacement depend upon the thickness (t) of the glass slab.i.e. D t for a given angle of incidence.

Light : It is the form of radiant energy which enables us to see the objects from whichit is reflected.

Longitudinal waves : It consists of compressions and rarefactions. In this types ofwaves the particles of the medium vibrate parallel to the direction of wave.

e.g. Sound waves in air.

Lateral inversion : In the mirror, in the image of the object the left side of objectappears as its right side and vice versa.

Mechanical waves / Elastic waves : Those waves which require material medium(solid/liquid/gas) for their propagation. e.g. Sound waves.

Normal :; A perpendicular drawn at the point of incidence.

Non-ohmic conductors : Those conductors which do not obey the ohms law. Its V-Igraph is curved. e.g. Diode-valve.

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Optical centre (O) : A fixed point inside the lens where a line drawn through the aperturemeets the principal axis.

Ohmic Conductors : Those conductors which obeys ohms law. Its V-I graph is astraight line.

Principal axis of a lens : A straight imaginary line joining the centre of curvatures oftwo spherical surfaces of the lens and passing through the optical centre of the lens.

Power of a lens (P) : It is the reciprocal of the focal length (in metre) of the lens.

P =1

f

Its S.I. unit is Dioptre (D)

Principal focus of a mirror : The point on the principal axis where the parallel rays oflight meet or appears to diverg after reflection.

Principal axis of a mirror : It is the straight line passing through the pole and the centreof curvature of the mirror.

Pole of a mirror : It is the centre of the reflecting surface of the spherical mirror.

Point of incidence (O) : The point where the incident ray strikes to the reflecting orrefracting surface.

Potential difference (V) : The potential difference between the two point in an electricfield is the amount of work done in moving a unit +(ve) charge from one point to another

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point.

i.e. Potential difference V =W

Q. Its S.I. unit is volt (V)

Pulse : A wave of short duration set up by a single disturbance in the medium. It isrepetitive in nature.

Rarer medium : A medium in which the speed of light is more or whose density isless.

e.g. Air is rarer than water : water is rarer than glass.

Reflected ray : The ray of light which is turned back by the mirror.

Refracted ray : ;A ray of light which deviates from its path on entering in anotheroptical medium.

Refraction of light : The bending of light when passes from one medium to anothermedium.

Radius of curvature (R) : It is the radius of the sphere of which mirror or lens is a part.

Real image : It is the image of the object formed if the rays actually meet at a point afterreflection or refraction. It can be obtained on a screen.

Reflection of light : It is the turning back of light in the same medium after striking thereflecting surface.

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Regular reflection : Reflection of light along a definite direction when falls on highlypolished and smooth surface.

Resistance (R) : It is the property of a conductor due to which it opposes flow of currentthrough it. Its S.I. unit is ohm (W).

Rarefactions (R) : The part of the longitudinal waves where the particles of the medium

are farther apart than normal.

Refraction of light : It is the change in direction of light when it passes from one

medium to another.

Reflection of sound : The bouncing back of sound when it strikes the hard surfacessuch as wall.

Specific heat of a substance : It is the quantity of heat required to raise the tempera-ture of unit mass of a substance by unit C.

Troughs : It is the depression in a transverse wave

Time period (T) : It is the time required to produce one complete wave. It is measuredin second (s).

Transverse waves : It consists of crests and troughs. In this waves the particles of

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the medium vibrate right angles to the direction of wave.

e.g. Light waves

Temperature : The quantity which helps in measuring the degree of hotness or cold-ness of a substance. Its S.I. unit is kelvin (k). In C.G.S. system its unit is degree celsius(C).

Ultrasonics : Sound waves having frequency greater than 20,000 Hz.

Virtual image : It is the image of the object formed if the rays do not actually meet ata point but appear to meet after reflection or refraction. It cannot be obtained on a screen.

Wavelength (l) : It is the distance between the two consecutive crests or between twoconsecutive troughs in transverse waves and between two consecutive compressions orbetween two consecutive rarefactions in longitudinal waves.

It is measured in cm/m.

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