PHOTOELECTRIC EFFECT CLASS 12 SOLUTIONS NOTES PDF

 

CLASS 12 

NCERT 

CHAPTER 11 

DUAL NATURE OF RADIATION AND MATTER SOLUTIONS

PHYSICS 

PHOTOELECTRIC EFFECT

 

The energy flux of sunlight reaching the surface of the earth is 1.388 × 10^3 W/m^2. How many photons (nearly) per square metre are incident on the Earth per second? Assume that the photons in the sunlight have an average wavelength of 550 nm.

The number of photons emitted per second by a Medium wave transmitter of 10 kW power, emitting radiowaves of wavelength 500 m. (b) The number of photons entering the pupil of our eye per second corresponding to the minimum intensity of white light that humans can perceive (10^10 W m^–2). Take the area of the pupil to be about 0.4 cm^2 , and the average frequency of white light to be about 6 × 10^14 Hz.

A 100W sodium lamp radiates energy uniformly in all directions. The lamp is located at the centre of a large sphere that absorbs all the sodium light which is incident on it. The wavelength of the sodium light is 589 nm. (a) What is the energy per photon associated with the sodium light? (b) At what rate are the photons delivered to the sphere ?

 

 

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 BEATS (SOUND) NUMERICALS DERIVATION CONCEPT \ MAHARASHTRA BOARD CLASS 12 PHYSICS SOLUTION

 

 
A set of 8 tuning forks is arranged in a series of increasing order of frequencies. Each fork gives 4 beats per second with the next one and the frequency of last fork is twice that of the first. Calculate the frequencies of the first and the last fork.
[Ans: 28 Hz, 56 Hz]

A sonometer wire is stretched by tension of 40 N. It vibrates in unison with a tuning fork of frequency 384 Hz. How many numbers of beats get produced in two seconds if the tension in the wire is decreased by 1.24 N?
[Ans: 12 beats]

 

 

photoelectric effect practice questions worksheet pdf with solutions

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  NCERT CLASS 11 PHYSICS CHAPTER 15 SOLUTIONS

 

 

 

 

15.14 A wire stretched between two rigid supports vibrates in its fundamental mode with a frequency of 45 Hz. The mass of the wire is 3.5 10-2 kg and its linear mass density is 4.0 10-2 kg m-'. What is (a) the speed of a transverse wave on the string, and (b) the tension in the string?

 15.15 A metre-long tube open at one end, with a movable piston at the other end, shows resonance with a fixed frequency source (a tuning fork of frequency 340 Hz) when the tube length is 25.5 cm or 79.3 cm. Estimate the speed of sound in air at the temperature of the experiment. The edge effects may be neglected.

15.16 A steel rod 100 cm long is clamped at its middle. The fundamental frequency of longitudinal vibrations of the rod are given to be 2.53 kHz. What is the speed of sound in steel?


15.17 A pipe 20 cm long is closed at one end. Which harmonic mode of the pipe is resonantly excited by a 430 Hz source ? Will the same source be in resonance with the pipe if both ends are open? (speed of sound in air is 340 m s-'). 

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