Tag: physics

Quizzes (598) Questions (13441)

Questions Related to physics

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

Find out the wavelength of violet light which has a frequency of $7.5 \times 10^{14}Hz$ ?

  1. $2.25\times 10^{23}m$

  2. $2.5\times 10^{5}m$

  3. $4\times 10^{-7}m$

  4. $7.5\times 10^{-7}m$

  5. $2.25\times 10^{7}m$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Given :    $\nu = 7.5 \times 10^{14}$  Hz

Speed of violet light (EM wave)     $v = 3 \times 10^8$ m/s
Thus wavelength of violet light         $\lambda = \dfrac{v}{\nu}  = \dfrac{3 \times 10^8}{7.5 \times 10^{14}}  =4 \times 10^{-7}$ m

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

In an electromagnetic spectrum, identify which of the following lists are ordered from longest wavelength to shortest wavelength?

  1. X ray, ultraviolet, visible light

  2. visible light, ultraviolet , X-ray

  3. ultraviolet, X-ray, visible light

  4. ultraviolet, visible light, X-ray

  5. X-ray, visible light, ultraviolet
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Decreasing order of wavelength :

 Visible light > ultraviolet > X-ray
Thus option B is correct.

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

The sun delivers $10^3\, Wm^{-2}$ of electromagnetic flux on the earth's surface. The total power that is incident on a roof of dimensions $6 \,m \times 30\, m$ is 

  1. $1.8 \times 10^5\, W$

  2. $7.2 \times 10^5\, W$

  3. $0.9 \times 10^5\, W$

  4. $4.5 \times 10^5\, W$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Given, electromagnetic flux $=10^3\, Wm^{-2}$
The area of roof $A= 6\, m \times 30\, m$
$=180 \, m^2$
The total power incident on roof
$P=10^3 \times 180$
$=1.8\times 10^5 \, W$

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

Photons of an electromagneitc radiation has an energy $11keV$ each. To which region of electromagnetic spectrum does it belong?

  1. $X-ray\ region$

  2. $Ultra\ violet\ region$

  3. $infrared\ region$

  4. $visible\ region$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

1 eV = (1.6 x 10^-19 coulomb) x (1 volt)

= 1.6 x 10^-19 joule

15 keV = 18 x 10^-16 J …..(a)

Given that photon energy = hf = 15 keV

hf = hc/lambda …… (b)

Now hc = (6.63 x 10^-34 J-sec) x (3 x 10^8 m/sec)

= 19.89 x 10^-28 J-m …..(c)

From (b), lambda = hc/15 keV and from (a) & (c)

Lambda = (19.89 x 10^-28 J-m)/(18 x 10^-16 J)

= 1.105 x 10^-12 m

= 0.01105 Angstrom, which is in the x-ray range