Title Edexcel-AS-Physics-Unit-2-All-6-Marks-Questions ✅

To explain this effect, Einstein proposed that electromagnetic radiation should be modelled as a particle rather than as a wave. Explain why, when considering the photoelectric effect, treating electromagnetic radiation as a particle is a more successful model than treating electromagnetic radiation as a wave. • Release of electrons is instantaneous. • If the wave model were correct, (energy) would take time to build up before electrons were released. • (Kinetic) energy of released electrons dependent on frequency. • If the wave model were correct, the (kinetic) energy of the released electrons would be dependent on the intensity. • Minimum / threshold frequency required to release electrons. • For waves, any frequency would be able to release electrons. - Compiled by Raiyad Reza Jan 2019 Helium was discovered in the 1860s by observing the spectrum produced by sunlight. An intense spectral line was seen, which did not correspond with any elements known at the time. Explain how specific spectral lines are produced by a hot gas • There are discrete energy levels. • Atoms/electrons (gain energy and) move to higher energy levels. • Atoms/electrons then move to lower energy levels (accept ground state) and a photon is emitttted • The energy of a photon if proportitional to its frequency. • The energy of the photon is equal to the difference in energy levels • There are specific frequencies emitttted because the energy differences • are specific June 2019 In 1921, Albert Einstein was awarded the Nobel Prize for Physics “for his discovery of the law of the photoelectric effect”.
A potential divider circuit can be created by making connections to a secondary circuit across the resistor (XY) or across the thermistor (YZ). As the temperature changes, the potential differences (p.d.) across XY and YZ both change. Such a circuit can be used to operate an air conditioning unit in a hot classroom in order to keep the classroom cool. The air conditioning unit starts operating when the p.d. in the secondary circuit exceeds a certain value. Explain how the circuit should be set up to keep the classroom cool. Your answer should include details of how a negative temperature coefficient thermistor works, in terms of particles. • When temperature is higher, greater energy to electrons (in thermistor) • When temperature is higher, more conduction/free electrons • When temperature is higher, lower resistance in thermistor • Decreased p.d. across thermistor / YZ Or current in circuit/thermistor increases • Increased p.d. across fixed resistor Or increased p.d. across XY • So for the air conditioning application, secondary circuit should be across XY October 2019 The circuit shown includes a fixed resistor and a negative temperature coefficient thermistor.
A pulse‐echo technique, using ultrasound, can be used to produce images of an unborn baby as shown. Explain how the ultrasound scan of the unborn baby is produced. • Ultrasound is reflected from boundaries/baby • (This reflection is caused by) change in density • Time taken between pulse being sent and received measured • Speed of ultrasound is known • Speed = distance/time can be used (to calculate the distance to boundary) • This information is fed in a computer system that is programmed to transfer this information into an image Jan 2020
For a particular passenger in an aircraft, the noise from the engine travels as a wave towards the passenger from the front. An ANR system creates a second sound wave that is directed towards the passenger from the side, as shown. Explain how this can lead to the sound being cancelled for one ear but louder for the other ear. • Sound (from ANR) has to diffract to reach the furthest/right ear • (Sound) cancelled when destructive interference takes place • (Sound) louder when constructive interference takes place • Destructive interference is where waves are in antiphase • Constructive interference is where waves are in phase • When distance between the ears is half a wavelength Or distance between the ears is approximately 20cm June 2020