1. Light with an average flux of \(20\, \text{W}/cm^2\) falls on a non-reflecting surface at normal incidence having surface area \(20\,cm^2\). The energy recieved by the surface during time span of 1 minute is

(1).\(12 \times\ 10^3\) J

(2). \(24 \times\ 10^3\) J

(3). \(48 \times\ 10^3\) J

(4). \(10 \times\ 10^3\) J

2. A radiation of energy ‘E’ falls normally on a perfectly reflecting surface The momentum transferred to the surface is (C = Velocity of light):

(1).\(\displaystyle \frac{E}{C}\)

(2). \(\displaystyle \frac{2E}{C}\)

(3). \(\displaystyle \frac{2E}{C^2}\)

(4). \(\displaystyle \frac{E}{C^2}\)

3. The electric field in a plane electromagnetic wave is given by
\(\text{E}_\text{z}\,=\,60\, \text{cos}\left(5\text{x}\,+\,1.5 \times 10^9 \text{t}\right)\,\text{V/m}\).
Then the expression for the corresponding magnetic field is (here subscripts denote the direction of the field):

(1).\(\text{B}_\text{y}\,=\,60\, \text{sin}\left(5\text{x}\,+\,1.5 \times 10^9 \text{t}\right)\,\text{T}\)

(2). \(\text{B}_\text{y}\,=\, 2\times 10^{-7}\,\text{cos}\left(5\text{x}\,+\,1.5 \times 10^9 \text{t}\right)\,\text{T}\)

(3). \(\text{B}_\text{x}\,=\, 2\times 10^{-7}\,\text{cos}\left(5\text{x}\,+\,1.5 \times 10^9 \text{t}\right)\,\text{T}\)

(4). \(\text{B}_\text{z}\,=\,60\, \text{sin}\left(5\text{x}\,+\,1.5 \times 10^9 \text{t}\right)\,\text{T}\)

4. An electron (mass \(9 \times 10^{-31} \text{kg}\) and charge \(1.6 \times 10^{-19}\text{C}\)) moving with speed c/100 (c = speed of light) is injected into a magnetic field \(\vec{\text{B}}\) of magnitude \(9 \times 10^{-4}\text{T}\) perpendicular to its direction of motion. We wish to apply an uniform electric field \(\vec{\text{E}}\) together with the magnetic fiekd so that the elctron does not deflect from its path. Then (speed of light c = 3 \times 10^8 \text{ms}^{-1}\))

(1).\(\vec{\text{E}}\) is parallel to \(\vec{\text{B}}\) and its magnitude is \(27 \times 10^4 \text{V m}^{-1}\)

(2). \(\vec{\text{E}}\) is perpendicular to \(\vec{\text{B}}\) and its magnitude is \(27 \times 10^4 \text{V m}^{-1}\)

(3). \(\vec{\text{E}}\) is perpendicular to \(\vec{\text{B}}\) and its magnitude is \(27 \times 10^2 \text{V m}^{-1}\)

(4). \(\vec{\text{E}}\) is parallel to \(\vec{\text{B}}\) and its magnitude is \(27 \times 10^2 \text{V m}^{-1}\)

5. A parallel plate capacitor made of circular plates is being charged such that the surface charge density on its plates is increasing at a constant rate with time. The magnetic field arising due to displacement current is:

(1).Zero between the plates and non-zero outside

(2). Zero at all places

(3). Constant between the plates and zero outside the plates

(4). Non-zero everywhere with maximum at the imaginary cylindrical surface connecting peripheries of the plates