PhysicsKund Physics class 9 to 12 NCERT, JEE - NEET

Experiment 8 : To find the refractive index of a liquid using a concave mirror and a plane mirror. AIM :  To find the refractive index of any liquid (water) using a concave mirror. APPARATUS :  A concave spherical mirror, water, an optical needle, a clamp stand, one meter scale, plumb line, etc. THEORY :  If the tip of object needle $O$ is at the centre of curvature $C$, the tip of the image will exactly coincide with it. ( Principle axis is verticle to the plane ). When water is filled in the concave mirror, the object needle is moved to a new position $C'$ to remove the parallax between the tips of the object needle and its image. A ray starting from $C$ reaches $E$ without deviation because it is along the radius of curvature. Due to water in the concave mirror the position of object and image shifts to $C'$.i.e now ray starting from $C'$ after refraction moves along $ED$ and then  $DC$ to make the apparent centre of curvature. $\angle NDC'=i \text{(incidence angl...

Experiment 5 : To determine the angle of minimum deviation for a given prism by plotting a graph between angle of incidence and angle of deviation. Aim :  To determine the angle of minimum deviation for a given prism by plotting a graph between angle of incidence and angle of deviation. Apparatus :  A glass prism, drawing boards, white sheet of paper, paper pins, drawing pins, half metre rod and a protector, a drawing board. Theory :  A prism is a wedge-shaped body made from a refracting medium (glass) bounded by two plane faces inclined to each other at some angle. A ray PQ incident on face AB of prism ABC making angle of incident i and is refracted along QR making angle of refraction $r_1$. At point R, the ray is refracted along RS making angle of emergence e and angle of refraction $r_2$ an shown in Fig. A is angle of prism and $\delta$ is angle of deviation . It can be proved that$ $A + \delta = i + e$ and $A = r_1 + r_2$ At minimum deviation ($\delta = \delta_m$) $i ...

Experiment 6 : To determine refractive index of a glass slab using travelling microscope. Aim :  To determine refractive index of a glass slab using travelling microscope. Apparatus :  Travelling microscope, a glass slab, lycopodium powder, spirit level. Theory :  When an object mark X is placed at the bottom of the glass slab of refractive index n, it appears to be raised, when viewed obliquely. The actual depth of the mark X is called real depth and the raised depth is called apparent depth. $\therefore$ Refractive index of the glass slab $n= \frac{Real  \ depth}{Apparent \ depth}$ Procedure Calculate the vernier constant of the travelling microscope. Level the travelling microscope using a spirit level and the base screws. Set its axis to the vertical scale. Move the eye piece of the microscope so that a sharp image of the cross-wires is obtained. Put an ink mark X on the plateform of the travelling microscope (M) and focus the microscope on it. Note the reading $...

Experiment 6 :  To find the frequency of the A.C. mains with a sonometer (and an electromagnet). Aim :  To find the frequency of the A.C. mains with a sonometer (and an electromagnet). Apparatus :  A sonometer with a soft iron wire stretched over it, an electromagnet, a step down transformer, slotted half kilogram weights, a hanger, physical balance and a weight box. Theory :  When a wire of length l having mass m per unit length under tension T is made to vibrate, its fundamental frequency is given by : $n = \frac{1}{2l} \sqrt{\frac{T}{m}}$ When AC is passed in the coil of electromagnet, it is magnetised twice in every cycle, first with one of its face as N-pole and then with same face as S-pole. If the electromagnet is held close to the middle of the sonometer wire (Fig. 4.4), the wire will be attracted twice during each cycle towards the electromagnet and forced vibrations are produced. If the length of the sonometer wire between two wedges is so adjusted that it ...

Experiment 4: To determine resistance of a galvanometer by half deflection method and to find its figure of merit AIM :  To determine resistance of a galvanometer by half deflection method and to find its figure of merit Apparatus :  Moving coil galvanometer, two resistance boxes, two one way keys, connecting wires, sand paper and a battery. Theory :  Connect the galvanometer whose resistance is to be determined in series with a high resistance R as shown in Fig. 2.5. Close key K₁, keeping key K₂ open. If I current pass through the galvanometer, Then $I_g = \frac{E}{R+G}$ If $\theta$ is the deflection produced in the galvanometer, then $\frac{E}{R+G} = k\theta \quad \ldots \text{(i)}$ Now key $K_2$ is closed and shunt S is so adjusted that the deflection is $\frac{\theta}{2}$ If $I_g'$ is the current flowing through the galvanometer at this stage, then $I_g' = \frac{k\theta}{2} \quad \ldots \text{(ii)}$ At this stage, total resistance in the circuit $R' = R + \frac{GS}{G...

Experiment 3 (b) : To verify the laws of combination (parallel) of resistances using a metre bridge. Aim :  To verify the laws of parallel combination of resistances using meterbridge. Apparatus Required: a) Metrebridge. b) Two resistance wires. c) Resistance box. d) One-way key. e) Jockey. f) Galvanometer. g) Battery eliminator. Theory: A meterbridge works on the principle of Wheatstone's bridge. According to this principle of four resistances P, Q, R, S are connected & formed a closed network ABCD & a cell is connected between A & C, then galvanometer will show no deflection when bridge is balanced. To get balanced condition, P, Q, R & S should be adjusted. In balanced condition $\frac{P}{Q} = \frac{R}{S} \quad \text{— (1)}$ If unknown resistance 'X' is connected in the right gap of meterbridge & null point is obtained at a distance 'l' from left end of meterbridge. then Q is considered as X R is considered as l Hence, R will be considered as (...

Experiment 3 (a) : To verify the laws of combination (series) of resistances using a metre bridge. Aim: To verify the laws of combination (series) of Resistance using a Metre Bridge Apparatus: A metre bridge, a Leclanche cell (battery eliminator), a galvanometer, a resistance box, a jockey, two resistance wire or two resistance coils known resistances, a set square, sand paper and connecting wires. Theory: (i) The resistance (r) of a resistance wire or coil is given by  $r = \frac{(100-l)R}{l}$ where R is the resistance from the resistance box in the left gap and l is the length of the metre bridge wire from zero end upto balance point. (ii) When two resistance $r_1$ and $r_2$ are connected in series then their combined resistance $R_S = r_1 + r_2$ Procedure : Mark the two resistance coils as $r_1$ and $r_2$. To find $r_1$ and $r_2$ proceed same way as in experiment 1. Connect the two coils $r_1$ and $r_2$ in series as shown in figure in the right gap of metre bridge and find the r...

Experiment 2 : To find resistance of a given wire / standard resistor using metre bridge. Aim :  To find resistance of a given wire using Whetstone’s bridge (meter bridge) & hence determine the specific resistance of the material. Apparatus : A meter bridge (slide Wire Bridge), a galvanometer, a resistance box, a laclanche cell, a jockey, a one- way key, a resistance wire, a screw gauge, meter scale, set square, connecting wires and sandpaper. Theory :  Metre bridge apparatus is also known as a slide wire bridge. It is fixed on the wooden block and consists of a long wire with a uniform cross-sectional area. It has two gaps formed using thick metal strips to make the Wheatstone's bridge. Then according to Wheatstone's principle, we have: $$\frac{X}{R} = \frac{l}{(100-l)}$$ The unknown resistance can be calculated as: $$X = R \frac{l}{(100-l)}$$ Then the specific resistance of the material of the is calculated as: $$\rho = \frac{X.\pi.D^{2}}{4L}$$ Where,  * L is the le...

Experiment 1: To determine resistivity of two / three wires by plotting a graph for potential difference versus current. Objective: To determine the resistivity of two wires by plotting a graph for potential difference versus current. Required Apparatus :  Two resistance wires, a voltmeter (0-3)V and an ammeter (0-3 se) A of appropriate range, a battery/battery eliminator, a rheostat, a meter scale, a one-way key, connecting wires, and a screw gauge. Theory / Formulae According to Ohm’s Law: $V \propto I \Rightarrow V = IR \Rightarrow R = \frac{V}{I}$ Resistivity \rho is given by: $\rho = \frac{R \cdot A}{L}$ where: R: resistance from V-I graph $A = \pi r^2 = \frac{\pi d^2}{4}$ : cross-sectional area L : length of the wire Circuit Diagram :  Observations: Range of ammeter = (0 – 3) A The least count of ammeter = 0.05 A Range of voltmeter = (0 -3) V The least count of voltmeter = 0.05 V The least count of metre-scale (L....

Experiment 9 : I-V Characteristics of a P-N Junction Diode in Forward and Reverse Bias  Aim: To study and plot the current-voltage (I-V) characteristics of a p-n junction diode under forward bias and reverse bias conditions. Apparatus Required: P-N junction diode DC regulated power supply Resistor (1 kΩ) Voltmeter (0–2V range) Ammeter (0–100mA for forward bias, 0–1mA for reverse bias) Breadboard or connecting wires Theory: A p-n junction diode allows current to pass primarily in one direction. It acts as a rectifier, blocking current in the reverse direction. Forward Bias: In forward bias, the p-side is connected to the positive terminal and the n-side to the negative terminal of the power supply. This reduces the potential barrier and allows significant current flow once the forward voltage exceeds a certain threshold (~0.7V for silicon). Reverse Bias: In reverse bias, the p-side is connected to the negative terminal and the n-side to the positive...

 Object : To establish the relation between the loss in weight of a solid fully immersed in (i) Tap water (ii) Strongly salty water , with the weight of water displaced by it by taking two different solid. Apparatus : Spring balance , steel or brass Bob , graduated measuring cylinder , thread , water , clamp stand and a Eureka can ( a glass or metallic container with a spout. Theory : Archimede's principle states that when an object is immersed wholly or partially in a liquid , it experiences an upward force which is equal to the weight of the liquid displaced by it. Apparent loss of weight of solid in water = weight of water displaced by the solid. Diagram :  Observation :  Weight of the bob ( made of steel or brass ) in air , W1 = ........ gmt. Weight of the bob when dipped in water , W2 = ....... gwt Apparent loss of weight of bob in water = W1 - W2 = ...... gwt Density of water at 4°C ( From tables ) = 1 g/cm3 Volume of water collected in the measuring cylinder , V = ...

Experiment : To determine the density of solid ( Denser than water ) by using a spring balance and a measuring cylinder. Apparatus : Metallic block or a cylinder , fine cotton thread , a spring balance measuring cylinder , beaker , water and a clamp stand. In place of metallic cylinder , brass or steel Bob can also be taken. Theory : Density of a substance is defined as mass of a unit volume of the substance. Density = mass / Volume The SI unit of density is $kg/m^{3}$ Diagram : Observation :  Least count of spring balance = ........ g Mass of metallic cylinder using spring balance  (i) m1 = ........ g     (ii) m2 = ......... g Mean mass of the metallic cylinder= m1+m2 / 2 = ......... g Calculations :  Mean mass of the cylinder , m = .......g Mean volume of the cylinder , V = ...... $cm^{3}$ Hence , density of the solid = m/V = ..... $g/cm^{3}$ Result : The Density of solid = ....... $g/cm^{3}$ Precautions : 1. The metallic cylinder should be clean and dry....

Object : To verify the laws of Reflection of sound . Apparatus : Two metallic or cardboard tubes , stopwatch, Drawing board , plastic screen , protractor , chalk piece and a pencil. Theory : When sound is incident on wood , brick or a plaster wall , it returns back. The returning back of sound after striking a hard surface is called reflection of sound. Sound waves obey the laws of Reflection which are as follows :  1. The angle of incidence is equal to the angle of reflection. 2. Incident wave , reflected wave and the normal lie in the same plane. Diagram :  Observations :  Result : 1. Angle of incident sound wave = Angle of reflected sound wave. 2. Sound wave , normal and the reflected sound all lie in same plane. Precautions:   1. Careful measurement of angle should be done by using protractor. 2. Table top should be horizontal and the wooden board should be vertically placed. 3. The stopwatch should be placed near the end of tube placed on the left-hand side. 4...