Nature of Electromagnetic Radiation

Q.

The frequency of yellow light having wavelength 600 nm is

1. $5.0\times {10}^{14}Hz$

2. $2.5\times {10}^{7}Hz$

3. $5.0\times {10}^{7}Hz$

4. $2.5\times {10}^{14}Hz$

Q.

Name any four regions of the electromagnetic spectrum in increasing order of frequency.

Q.

In vacuum all types of electromagnetic radiations, regardless of wavelength, travel at the same speed.

1. True

2. False

Q.

What is the difference between PWM and PPM?

Q. Choose the correct values of wavelength and frequency of a light wave whose time period is $2\times {10}^{-10}s$.

1. Frequency = $5\times {10}^9{s}^{-1}$,
   wavelength = $6\times {10}^{-2}m$
2. Frequency = $5\times {10}^9{s}^{-1}$,
   wavelength = $2\times {10}^{-2}m$
3. Frequency = $1.67\times {10}^9{s}^{-1}$,
   wavelength =$6\times {10}^{-2}m$
4. Frequency = $5\times {10}^3{s}^{-1}$,
   wavelength =$6\times {10}^{-2}m$

Q.

An anchored boat is rocked by waves whose crests are 100 m apart and whose velocity is 25 m/s. How often do the crests reach the boat?

1. 0.35 s

2. 4 s

3. 75 s

4. 2500 s

Q.

Frequency is defined as the distance between two neighbouring crests or troughs of a wave.

1. True

2. False

Q. An electromagnetic radiation of wavelength 242 nm is just sufficient to ionize a sodium atom. The ionization energy of sodium in $kJmo{l}^{-1}$ is .

1. 394.5
2. 494.5
3. 594.5

Q.

An Electromagnetic radiation of wavelength 242 nm is just sufficient to ionize a sodium atom. Calculate the ionization energy of sodium in kJ ${mol}^{-1}$.

1. 294.5KJ ${mol}^{-1}$

2. 394.5 KJ ${mol}^{-1}$

3. 494.5KJ ${mol}^{-1}$

4. 594.5KJ ${mol}^{-1}$

Q. The size of corpuscles for different colours will be:

1. Same
2. Different
3. Either (a) or (b)
4. None of these

Q.

The frequency of yellow light having wavelength 600 nm is

1. $5.0\times {10}^{14}Hz$

2. $2.5\times {10}^{7}Hz$

3. $5.0\times {10}^{7}Hz$

4. $2.5\times {10}^{14}Hz$

Q. A 600 W mercury lamp emits a monochromatic radiation of wavelength 331.3 nm. How many photons are emitted from the lamp per second?
$h=6.626\times {10}^{-34}\text{Js};\text{velocity of light =}3\times {10}^8{\text{ms}}^{-1}$

1. ${10}^{21}$
2. ${10}^{22}$
3. ${10}^{20}$
4. ${10}^{19}$

Q. If a source is transmitting electro-magnetic waves of frequency $8\times {10}^{6}Hz$, then the wavelength (in m) of the electro-magnetic waves transmitted from the source will be:

1. 20.90 m
2. 23.50 m
3. 12.50 m
4. 37.50 m

Q. Statement - 1: The difference between two adjacent crests is called wavelength.
Statement - 2: Frequency is defined as number of waves that pass a given point in one second.
Statement - 3: The maximum displacement shown by a point on a wave measured from its equivalent position is called wave number.

1. TTT
2. FTT
3. TTF
4. FFT

Q.

A gas absorbs a photon of 355 nm and emits two wavelengths. If one of the emission is at 680 nm, the other is at:

1. 518 nm

2. 1035 nm

3. 325 nm

4. 743 nm

Q.

A bulb emits light of wavelength 4500 $\mathring{A}$. The bulb is rated as 150 W and 8% of the energy is emitted as light. How many photons are emitted by the bulb per second?

1. 2.715 $\times$ ${10}^{19}$

2. 4.715 $\times$ ${10}^{19}$

3. 5.615 $\times$ ${10}^{19}$

4. 7$\times$ ${10}^{19}$

Q. Which of the following statements are correct regarding polarization of light?

1. A light wave vibrating in more than one plane is called as unpolarized light
2. A light wave vibrating in more than one plane is called as polarized light
3. A polarized light wave is a form of sound wave
4. A polarizer is a device which is used to transmit a wave vibrating in a single plane to a wave vibrating in more than one plane.

Q. Choose the correct values of wavelength and frequency of a light wave whose time period is $2\times {10}^{-10}s$.

1. Frequency = $5\times {10}^9{s}^{-1}$,
   wavelength = $6\times {10}^{-2}m$
2. Frequency = $5\times {10}^9{s}^{-1}$,
   wavelength = $2\times {10}^{-2}m$
3. Frequency = $1.67\times {10}^9{s}^{-1}$,
   wavelength =$6\times {10}^{-2}m$
4. Frequency = $5\times {10}^3{s}^{-1}$,
   wavelength =$6\times {10}^{-2}m$

Q.

The wavelength range of the visible spectrum extends from violet (400 nm) to red (750 nm). Express these wavelength in frequencies (Hz). $(1nm={10}^{-9}m)$.

1. $4\times {10}^{14}to7.5\times {10}^{14}Hz$

2. $8\times {10}^{14}to16\times {10}^{14}Hz$

3. $7\times {10}^{14}to16\times {10}^{14}Hz$

4. $7.5\times {10}^{14}to16\times {10}^{14}Hz$

Q.

Wavenumber is defined as the number of wavelengths per unit length

1. True

2. False

Q. A certain radio station broadcasts on a frequency of 1890 kHz (kilohertz). What is the wavelength of the electromagnetic radiation broadcasted by the station?

1. 158.7 m
2. 100.5 m
3. 135.9 m
4. 88.2 m

Q.

An Electromagnetic radiation of wavelength 242 nm is just sufficient to ionize a sodium atom. Calculate the ionization energy of sodium in kJ ${mol}^{-1}$.

1. 294.5KJ ${mol}^{-1}$

2. 394.5 KJ ${mol}^{-1}$

3. 494.5KJ ${mol}^{-1}$

4. 594.5KJ ${mol}^{-1}$

Q.

The SI unit of frequency is __________.

Q.

A source of wave produces 40 crests and 40 troughs in 0.4 second. Find the frequency of the wave.

Q. A gas absorbs a photon of 355 nm and emits two wavelengths. If one of the emission is at 680 nm, the other is at .

1. 325 nm
2. 743 nm
3. 1035 nm