Sharp EL-5230, EL-5250 operation manual Radioactive decay, Decay Normal PROGRAM?

Chapter 8: Application Examples

Radioactive decay

Carbon-14 (14C) is a naturally occurring radioactive isotope of carbon used in the carbon dating process. Because carbon-14 decays at a steady rate, it is possible to determine the age of a once living specimen by measuring the residual amount of 14C it contains.

The mass of 14C contained in a sample changes according to the equation

				M1
				–ln ( ––– )
M = M0 e	–kt		or	M0
				t = –––––––––
				k
where M1		= Mass of 14C at time t
M0		= Original mass of 14C

k = Radioactive decay constant (for 14C, k = 1.2118 ⋅ 10–4year–1) t = Elapsed time in years

Example

This program asks for a original mass and current mass of 14C and tells you how old the specimen is. It then finds the half-life of 14C.

1.Press b 2 1 0 to open a window for creating a NEW program.

2.Type DECAY for the title then press e.

•A NEW program called ‘DECAY’ will be created.

3.Enter the program as follows.

DECAY :NORMAL PROGRAM?

Program code	Key operations
Print”ORIGINAL MASS	i 1 @ a ORIGINAL s
	MASS ; e
Input M≠	i 2 @ v M0 e e
	e
Print”CURRENT MASS	i 1 @ a CURRENT s
	MASS ; e
Input M≥	i 2 @ v d M1 e
	e e

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