Physics Waves And Oscillations Level: High School
Sound Level Intensity
A person standing a certain distance from an airplane with four equally noisy jet engine is feeling a sound level intensity bordering on pain, 120 dB . what sound level intensity (in dB) would this person experience if the captain shut down three engines ? Do not enter units .a) If the amplitude of a sound wave is doubled , by what factor will the intensity increase ?
b) By how many dB will the intensity level increase ?
Physics Waves And Oscillations Level: High School
Speed of Sound
A fishing boat is drifting just above a school of tuna on a foggy day . Without warming , an engine backfire occurs on another boat 1.02 km away , as seen in the figure at “click here” .a) How much time elapses between the instant when the backfire is heard by the fisherman ?
Physics Electromagnetic Induction Level: High School
One method of measuring the magnetic field strength uses a closely-wound coil of wire N turns and enclosing an area A . This coil is initially placed so that the flux ¥õ through the area is a maximum (see figure at ¡°click here¡±) .Then in a small time interval . Delta t is rotated ¨ù of a turn so that it is parallel to the magnetic field , and the flux through its area reduces to zero .a) Two leads from either end of the coil are connected to a machine that measures the amount of charge Q (Q = I delta f) if the total resistance of the coil and the charge measuring device is R , derive an equation for the charge Q in terms of N,A,R and the negative flux density B .
b) A closely wound coil containing 200 turns is 45 cm in radius and has a resistance of 60.0 ohm . It is placed in a magnetic field . and connected to a charge-measuring instrument . The coil is initially perpendicular with the magnetic field , and is quickly rotated by ¨ù turn so that it becomes aligned with the field ,and a charge of 45.7 micro C is measured . What is the magnetic flux density of the field ?
Physics Magnetism,Magnetic Effects Of Current Level: High School
Magnetic Flux
A 0.50 m length of wire has a current of 0.35 A passing through it .a) What is the magnitude flux density at a perpendicular distance of 1.2 cm from the wire ?
b) If the wire is bent into a circle , what will be the magnetic flux density at the centre of this circle ?
c) The same piece of wire is curled into a solenoid with 210 turns , and this solenoid is 3.0 cm long . What is the magnetic flux density at the centre of the solenoid ?
Physics Electrostatics Level: High School
Capacitance
John wants to replace the arrangement of capacitors shown in the figure at “click here” with a single capacitor such between points a and b the capacitance stays the same . What capacitance should this capacitor have ?C1 = 5 micro F , C2 = C3 = 4 micro F , C4 = 6 micro F .
Physics Electrostatics Level: High School
Capacitance
(i) The plates of a parallel-plate capacitor are in vacuum , 5.00 mm apart , and are circular in shape with a radius of 17.0 cm . The plates have charges of +- 37.4 micro C . what is the voltage across the plates and capacitance of the capacitor ?
(ii) In the above mentioned capacitor , a dielectric material, strontium titanate , is placed between the plates such that the voltage reduces to 750 V . What is the relative permittivity of the dielectric ?
Physics Electrostatics Level: High School
Gold Leaf Electroscope
(i) A force F exists between two charges , Q1 and Q2 that are a distance r apart . If charge Q1 is halved , and the distance r is increased by a factor of 4 , how much the charge Q2 be changed so that the force remains the same ?
(ii) A conducting rod is earthed while a negatively charged object is held next to one end (without touching it ) such that the rod becomes charged . This charged rod is then brought into contact with the gold-leaf electroscope . The conducting rod is then removed . As a result of this , will the gold leaves become further separated ,or become closer together. Justify your answer .
Physics Ray Optics Level: High School
Convex Lens
An object of 4 cm is placed 15 cm from a converging lens of focal length 10 cm as shown in Figure 3 at “click here” .Determine the image properties (where it is formed , height , real/virtual , magnified/diminished inverted/erect) using a ray diagram , as well as the lens formula .A second converging lens of focal length 15 cm is placed 36 cm behind the first lens as shown in figure 4 at “click here” . Describe the image formed in by this compound lens system . Again use a ray diagram as well as the lens formula .
Physics Ray Optics Level: High School
Canchy’s Formula
White light is incident at an angle of 30 degree on a triangular prism with apex angle 55 degree . For red light (lamda = 680 nm) the refractive index is 1.526 and for green light (lamda = 533 cm) the refractive index is 1.533 . What is the angle that the visible spectrum (red to violet) is spread over as it emerges from the prism ? (Hint : use Cauchy’s equation to determine the refractive index for violet light , lamda = 410 nm)
Physics Ray Optics Level: High School
Total Internal Reflection in a Prism
A periscope is made using the prism shown at “click here” to reflect the light rays through at 90 degree angle .What is the minimum possible refractive index the prism material must have in order for it to function as shown ? (Assume that the prism is in the air )
Discuss what will happen to the light ray if the refractive index of the prism is less than this value , and also what happens when the refractive index is increased ?
Physics Ray Optics Level: High School
Refraction
A beam of light with wavelength of 470 nm in vacuum is incident on a liquid of refractive index 1.37 at a glancing angle of 32 degree (see figure at “click here”)(i) What is the angle of refraction of the light ?
(ii) What is the wavelength of the light in the liquid ? (Hint : the frequency of light does not change in different media , however the velocity of the wave does , and for a wave the velocity and frequency are related as f lamda = v)
Physics Heat & Thermodynamics Level: High School
Conduction
Calculate the rate of heat transfer per unit are although a wall constructed of 12 mm fibro , 10.0 cm concrete and 15 mm of wood paneling if one side is at 17 degree C and the other is at 38 degree C .(K concrete = 0.96 , K fibro = 0.055 , K wood = 0.37 Wm-1K-1)
Physics Heat & Thermodynamics Level: High School
Thermal Expansion
In an winter (avg . temp 15 degree C) , Bob’s pendulum clock keeps time perfectly , where the pendulum has a period of 2 s , The pendulum shaft is a thin brass rod , which has a thermal expansion co-efficient of 2.0 x 10-5 K-1 , In one day , how much time will be lost /gained in the summer when the average temperature is 25 degree C ?The period of oscillation (T) for a pendulum of length l is given be ,
T = 2pi (sqrt g/g)
Where g is the acceleration due to gravity (g = 9.81 m/s2)
Physics Properties Of Matter Level: High School
Archimedes’s Principle
Jason has bought a ring , and wishes to confirm that it is made of silver . The ring weighs 70.0 g and Jason heats it up to 87.5 degree C . He then places it in a glass that contains 255 mL of water at room temperature (23 degree C) . The full glass weighs 330 g . The final temperature after thermal equilibrium is reaches is 24.0 degree C . What is the ring made out of ? ( C silver = 234 JkgK-1 , C nickel = 444 JkgK-1, C paladin = 244 JkgK – 1 ,density of water = 100 kg/m3,10Cm^3 = 1 L )
Physics Ray Optics Level: High School
Young’s Double Slit Experiment
Katrinal is using Young’s two-slit experiment to determine the separation and width of two slits . The wavelength of the light that is passed through the two slits is 590 nm . On the screen the separation of the bright fringes is 2.82 mm on a screen that is 2.20 m away . Katrina then blocks one of the slits and measures the distance from the central bright fringe to the first minima as 6.5 cm . What is the slit separation and the width of the slits ? (Hint : for small angles , sin theta = tan theta)