The sun is 150,000,000 km from earth; its diameter is 1,400,000 km. A student uses a 4.6-cm-diameter lens with f = 10 cm to cast an image of the sun on a piece of paper. What is the diameter of the image on the paper?

Explanation:

the image distance can be calculated using below formula of lens

1/v=1/- 1/u

Where

u= Object distance = 15×10^7km

Diameter = 1400000 km

Diameter of lens = 4.6 cm

f= Focal length ( 10 cm)= 1×10^-4

We can substitute to the above formula we have

1/15×10^7km+1/1×10^-4

V=0.001km

Therefore, paper stayed on the focus, hence the sharp image

answer: the correct answer is 1.

explanation: there are various process in which a radioactive nuclei decays:

1) alpha decay: in this process, a heavier nuclei decays into lighter nuclei by releasing alpha particle. the mass number is reduced by 4 units.

2) electron capture: in this decay process, a parent nuclei absorbs an electron and gets converted into a neutron. simply, a proton and an electron combines together to form a neutron. mass number does not change in this process.

3) gamma ray emission: it is a decay process in which an unstable nuclei gives excess energy by a spontaneous electromagnetic process. this decay releases . this process does not change the mass number.

4) positron emission: it is a type of decay process, in which a proton gets converted to neutron and an electron neutrino. this is also known as -decay. in this the mass number remains same.

from the above information, we see that only alpha-decay is producing a change in the mass number of the nucleus.

a) electrical > light, sound, and thermal< < < <

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c) both a and b.