(a) Define Radio-activity (2mks)
Radioactivity is the spontaneous disintegration of a nucleus releasing
alpha, beta and gamma radiations accompanied by the release of energy
(b) When carrying out experiments with radioactive substances the source should never be held with bare hands but with forceps. Explain? (1mk)
Radioactive substances are harmful to body cells when ingested
(i) Plot on the graph paper provided the graph of the count rate (y-axis) against time
(ii) From the graph, determine the half-life of Radon-220 (1mk)
Half-life of radon 220=54 sec + 2 (showing on graph a must)
(e) The diagram in the figure below shows paths taken by three radiations A,B and C from a radioactive isotope through an electric field.
(i) State the charge on plate Y (1mk)
(ii) Identify the radiations A and C (2mks)
(iii) Give a reason why C deviates more than A (1mk)
C more massive than A
The following is a part of a radio-active series
Identify the radiation r, find the values of c and d (3mks)
r is βeta particle
c is 206
d is 82
K.C.S.E Physics Q & A - MODEL 2019PP2QN19
(a) Define half life as used in radioactivity.
(b) Figure 13 shows a device used to detect radioactivity by forming tracks when air is ionised.
(i) State the name of the device shown.
FORM I - PHYSICS SYLLABUS
FORM II - PHYSICS SYLLABUS
FORM III - PHYSICS SYLLABUS
FORM IV - PHYSICS SYLLABUS
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