Q141 of 196 Page 249

One Fermi is equal to 10–15 metre. The radius of a proton is 1.3 Fermis. Write the radius of a proton in metres in standard form.

Given 1 Fermi = 10-15 m


Radius of proton = 1.3 Fermis


Radius of proton in metres = 1.3 × 10-15


Moving 1 decimal to the right,


⇒ 1.3 × 10-15 = 13 × 101 × 10-15


We know that by properties of exponents, am × an = am + n.


⇒ 13 × 101 × 10-15 = 13 × 101-15


= 13 × 10-14


∴ The radius of a proton in standard form is 13 × 10-14 m.


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