A60co source with activity 2.4×10−4 ci is imbedded in a tumor that has mass 0.550 kg . the source emits γ photons with average energy 1.25 mev. half the photons are absorbed in the tumor, and half escape.

a. what energy is delivered to the tumor per second?

b. what absorbed dose (in rad) is delivered per second?

c. what equivalent dose (in rem) is delivered per second if the rbe for these γ rays is 0.70?

d. what exposure time is required for an equivalent dose of 180 rem ?

(A). The energy delivered to the tumor per second is .

(B). The absorbed dose delivered per second is

(C). The equivalent dose delivered per second is

(D). The exposure time is 18 days.

Explanation:

Given that,

Activity of the source

Mass of tumor = 0.550 kg

Average energy = 1.25 MeV

Half the photons are absorbed in the tumor, and half escape

1 Gy =100 rad

(A). We need to calculate the energy delivered to the tumor per second

Using formula of energy delivered

Put the value into the formula

(B). We need to calculate the absorbed dose delivered per second

Using formula of absorbed dose

Put the value into the formula

(C). If the RBE for these γ rays is 0.70

We need to calculate the equivalent dose delivered per second

Using formula of  the equivalent dose

Put the value into the formula

(D). We need to calculate the exposure time for required for an equivalent dose of 180 rem

Using formula of exposure time

Hence, (A). The energy delivered to the tumor per second is .

(B). The absorbed dose delivered per second is

(C). The equivalent dose delivered per second is

(D). The exposure time is 18 days.

carbon is found in all living things. carbon atoms move constantly through

living organisms, the oceans, the atmosphere, and the earth’s crust in what is

known as the carbon cycle. the directions taken by carbon atoms through this

cycle are very complicated and can take millions of years to make a full circle.

all animals, from humans to the dinosaurs are part of the carbon cycle. when

animals eat food, they get carbon in the form of carbohydrates and proteins.

in animals, oxygen combines with food in the cells to produce energy for daily

activity and then gives off carbon. the carbon combines with oxygen to form

carbon dioxide (co2) and is released back into the atmosphere as a waste

product when animals breathe and exhale.

from 145-65 million years ago, earth was much

hotter than today and covered with dense,

tropical swamp forests. the trees and other

plants were immense and

provided an endless supply of

food for the giant animals that

roamed the land. somewhere in

the air above one of these

forests, a lone carbon atom has joined

up with two oxygen atoms to form a molecule of co2.

the co2 molecule was sucked into the tiny holes (stomata) on the leaf of a

fern plant and joined with sunlight, chlorophyll and water to make food and

energy in the plant’s cells through photosynthesis. the oxygen (o2) from the

co2 molecule was sent back into the atmosphere; the carbon atom (c) was

detached and used to make a molecule of sugar.

if that carbon atom had been eaten instead, a totally

different situation would have developed. let’s say

that a giant plant-eating dinosaur (herbivore) ate the

fern for breakfast, and swallowed the carbon in the

fern in the form of carbohydrates and proteins. in

the process of respiration, oxygen combined with

the carbohydrates and proteins in the dinosaur’s cells

to provide energy for its daily activity.  

answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.