UCE PHYSICS 2009 PAPER 2 QTN 5

a) Distinguish between thermionic and photoelectric emission.

(b)

Ultra violet radiations are incident on a clean zinc plate resting on the cap of a charged gold leaf electroscope as shown in figure 2. Explain what is observed if:

(i) The gold leaf electroscope is positively charged

(ii) Radio waves is used instead of ultra violet radiations

(c ) (i) with the aid of a labeled diagram, describe how X-rays are produced in an X-ray tube.

(ii)Explain why soft x-rays are used instead of hard X-rays to take photographs of internal parts of a patient in hospitals.

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