PHYSICS TESTLET V

ST. MARTIN’S GIRLS SCHOOL, KIBAGARE
P.O.BOX 14960-00800
FORMIV PHYSICS ASSIGNEMENT TUESDAY 15TH SEPTEMBER 2009
NAME: ______________________________________________________________
1. What is photoelectric effect?

2. The threshold frequency needed to eject an electron from a metal is 5.0x1014HZ. The metal surface is shone with a light of frequency 6.5 x 1014HZ. Determine
I) Maximum wavelength of light needed to emit electrons from the surface of the metal 3mks


II) Work function of the metal. 3mks


III) Maximum kinetic energy of the electrons ejected 3mks.


IV) The mass of an electron if the maximum speed of electron is 4.68 x 105 ms-1 3mks


3. Arrange beta gamma and alpha radioactive radiation in order of
i) Penetrating power.
ii) Ionizing power.
4. The radium nucleus emits alpha particle and changes to Radon. Complete the nuclear equation for this change by giving values of X and Y. 2mks
226 x 222
Ra α + Rn
88 2 Y
X=_________________ Y=___________________________
5. The diagram below shows a gold leaf electroscope designed to detect radiations from radioactive substance.









a) When the source of α-ray is brought close to the electroscope, the leaf collapses. Explain. 2mks

b) Why is a leaf electroscope not a good detector of beta particles and gamma rays? 1mk


c) What is the common aspect of nuclear fission and nuclear fusion?1MK