AQA 2022 PHYSICS AS LEVEL 7407 PAPER 1

A sigma-plus (Σ+) particle and an unidentified particle Y are produced by the strong interaction between a positive pion (π+) and a proton (p). This interaction is represented by the equation: π+ + p → Σ+ + Y . Complete Table 1 to show the baryon number B, charge Q and strangeness S for the particles in this interaction. [2 marks] Table 1 π+ p Σ+ Y B 0 Q +1 +1 +1 S +1 . Which particle in Table 1 has the quark structure uus? Tick () one box. [1 mark] π+ p Σ+ Y . Deduce which particle, π+ or Y, has the greater charge-to-mass ratio. Justify your conclusion. [3 marks] Do not write outside the box Turn over for the next question Turn over ► A sample of bromine gas contains a mixture of two isotopes. An experiment is done to find the percentage of each isotope in this sample. Do not write outside the box . In the experiment, the gas is ionised by a beam of electrons. Explain how the beam of electrons causes a particle of the gas to have a charge of +1e. [2 marks] The gas consists of bromine molecules. Each molecule has two bromine atoms. The experiment finds that the bromine molecules contain 158, 160 or 162 nucleons. Figure 1 shows the percentage of these different molecules in the sample. Figure 1 . Bromine has a proton number of 35 The two isotopes in the sample have different nucleon numbers. Calculate the number of neutrons for the isotope that has the greater nucleon number. [2 marks] number of neutrons = Do not write outside the box . Deduce the percentage of each isotope in the gas. Justify your conclusion. [2 marks] Turn over for the next question Turn over ► A satellite system is used to measure the height h of the top of an ice sheet above the surface of the ocean. The satellite emits two pulses A and B of infrared radiation. A is incident on the surface of the ocean and B is incident on the top of the ice sheet as shown in Figure 2. Figure 2 . The frequency of the infrared radiation is 3.8 × 1014 Hz. Each pulse has a duration of 6.0 ns. Do not write outside the box Calculate the number of cycles in each pulse. [2 marks] number of cycles = . A and B reflect and return to the satellite. The travel time is the time between the emission of a pulse and its return to the satellite. The difference in the travel times of A and B is 10.7 μs. Calculate h. [2 marks] h = m Some of the infrared radiation enters the ice sheet. Figure 3 shows the path of infrared radiation that refracts at a sloping part of the ice sheet. Figure 3 Do not write outside the box