Radar can be used to measure the distance from the sun to the earth.

a) the speed of the wave is 3x10^8 m/s and the distance to the sun is 1.496x10^8 km; how long should the signal take to reach the sun and come back?
b) why can’t sound waves be used in this situation?

1)  t = 16.6 minutes

2)  Sound waves need a medium for propagation.

Explanation:

Given,

The speed of the wave, v = 3 x 10⁸ m/s

The distance between Sun and the Earth, d = 1.496 x 10⁸ Km

                                                                         = 1.496 x 10¹¹ m

The speed and distance is given by the formula

                                             v = d/t

Or,                                        t = d / v

Substituting the values in the above equation

                                             t = 1.496 x 10¹¹ m / 3 x 10⁸ m/s

                                               = 498.67 s

                                              = 8.3 minutes

Since the radar requires the signals to come back. Therefore, the total distance the waves traveled is twice the distance between the Sun and the Earth.

The time taken by the waves to reach radar is

                                        t = 2 x 8.3 min

                                          = 16.6 min

Hence, time taken by the signal take to reach the sun and come back is, t = 16.6 min

The light waves do not require a medium for propagation. But the sound waves need a medium such as air, water, metal, or atmosphere for the propagation.

A vacuum exists beyond the outer space of the Earth's atmosphere. No mediums exist there.  

So, sound waves can't be used in this situation.

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.

jupiter is the largest planet in our solar system, having a mass and radius that are respectively, 318 and 11.2 times that of earth. suppose that an object falls from rest near the surface of each planet and that the acceleration due to gravity remains constant during the fall. each object falls the same distance before striking the ground. determine the ratio of the time of fall on jupiter to that on earth.