Question

Answer the following multiple choice questions.

The headlights are shining on a truck travelling at 90km/h. The speed of the light from the headlights relative to the road will be:

a) c

b) c + 90km/h

c) c - 90km/h

d) depends on the temperature, but faster than the speed if the truck was not moving

e) faster than if the truck was not moving, but impossible to calculate with the given information

Events may seem to take longer to an observer who is in motion with respect to an event

a) true

b) false

Light is shining on a metallic surface causing electrons to be ejected. Increasing the intensity of light:

a) causes ejected electrons to have more kinetic energy

b) causes ejected electrons to have less velocity

c) causes even more electrons to be ejected

d) causes no change to the ejected electrons or to the number of ejected electrons

e) none of the above

The greater the work function for a metal

a) the greater the speed of the ejected electron

b) the smaller the speed of the ejected electron

c) the more electrons are ejected

d) the lower the threshold frequency

e) none of the above

Time is

a) dependent on the observer

b) absolute

c) the same for different observers

d) simultaneous in all cases

e) never changing

In Newtonian mechanics, the speed of light can be infinite. True or false?

Answer 1

Answer __

(1) According to the Einstein`s theory of relativity the velocity of light is the maximum attainable velocity and not depend on the frame so the velocity of the light will remain c .

option (a) is correct .

(2 ) as we know that the time dilation phenomenon according to which moving clock ticks slowly . so the event will be longer for the observer in motion .

option (a) is correct .

(3) now this is from Photo - electric effect according to which when the light of frequency greater than the threshold frequency falls on the metal surface electron will ejected from the surface of the metal . and according to the experimental results when we increase the intencity of the light the number of the electron ejected from the metal increases . and on increasing the frequency the kinetic energy of the photo electron will increases .

so the option (c) is correct .

(4) the wok function of the metal = the minimum energy required to eject the electron from the surface = hv₀ so

the kinetic energy of the ejected electron is

so the greater the work function smaller the kinetic energy as well as the velocity of the ejected electron.

option (b) is correct .