A radioactive source produces gamma rays.
The diagram shows a detector and a piece of lead placed near the radioactive source.
The count rate is 3600 counts per minute (cpm)3600\text{ counts per minute (cpm)}3600 counts per minute (cpm) without the lead in place.
What could the count rate be with the 1.5 cm lead sheet in place?
0 cpm0\text{ cpm}0 cpm
950 cpm950\text{ cpm}950 cpm
3600 cpm3600\text{ cpm}3600 cpm
4800 cpm4800\text{ cpm}4800 cpm