A pushed dye laser emits light of wavelength 585 nm. Because this wavelength is strongly absorbed by the haemoglobin in the blood, the method is especially effective for removing various types of blemishes due to blood. To get a reasonable estimate of the power required for such laser surgery, we can model the blood as having the same specific heat and geat of vaporization as water. [`S=4.2xx10^(3)J(kgK)^(-1)`,`L=2.25xx10^(6)Jkg`]
Q. Suppose that each pulse must remove `2mug` of blood by evaporating it starting at `30^circ`C. The energy that each pulse must deliver to the blemish is nearly

Options

A. `5.1J`
B. `5.1mJ`
C. `5.1muJ`
D. `5.1kJ`

Answer

B

Explanation

Energy required,
`E=mstriangletheta+mL`
`=2xx10^(-9)xx4.2xx10^(3)xx70+2xx10^(-9)xx2.25xx10^(6)`
`=5.088xx10^(-3)J` `=3.18xx10^(16)eV`