Tag: physics

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Multiple choice physics stationary waves formation of stationary waves stationary waves and its graphical representation standing waves in strings from moving to stationary stationary (or standing) waves

The equation, $Y=0.02 sin (500 \pi t) cos(4.5x)$ represents

  1. progressive wave of frequency 250 Hz along x-axis

  2. a stationary wave of wavelength 1.4 m

  3. a transverse progressive wave of amplitude 0.02 m

  4. progressive wave of speed of about $350ms^{-1} $
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Comparing the given wave equation with standard standing wave equation
$y (x, t) = A \sin (\omega t)\cos (kx)$, 


we get, $k =4.5$

$k = \dfrac{2\pi}{\lambda}$

$\Rightarrow \lambda = \dfrac{2\pi}{k} =1.4$ $m$

Multiple choice physics stationary waves formation of stationary waves stationary waves and its graphical representation standing waves in strings from moving to stationary stationary (or standing) waves

The equation of a progressive wave is $y=4\,sin(4\pi t-0.04x+\dfrac{\pi}{3})$ where x is in metre and t is in second. The velocity of the wave is

  1. $100\pi\,m/s$

  2. $50\pi\,m/s$

  3. $25\pi\,m/s$

  4. $\pi\,m/s$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The equation of the progressive wave is given as, $y=4\,sin(4\pi t-0.04x+\dfrac{\pi}{3})$.

The velocity of the wave would be equal to

$\dfrac{\omega}{k}=\dfrac{4\pi}{0.04}=100\pi\;m/s$

Multiple choice physics stationary waves formation of stationary waves stationary waves and its graphical representation standing waves in strings from moving to stationary stationary (or standing) waves

Which of the following statements are correct?

  1. A wave front is a locus of points vibratig in same phase

  2. Wavelength is separation between two consecutive points vibrating in same phase

  3. For two sources to be coherent their frequencies must be same

  4. All of the above statements are correct.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A wavefront is indeed a locus of points in the same phase. Wavelength is the distance between consecutive points in the same phase. Coherent sources must have the same frequency and constant phase difference.

Multiple choice electromagnetic spectrum electromagnetic waves physics

The matter-wave picture of electromagnetic wave/radiation elegantly incorporated the:

  1. Heinsenbergs uncertainty principle

  2. correspondence principle

  3. cosmic theory

  4. Hertzs observations
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The matter-wave picture of electromagnetic wave/radiation elegantly incorporated  the Heisenberg uncertainty principle.

The correct option is A.

Multiple choice electromagnetic spectrum electromagnetic waves physics

If $c$ is the speed, $\nu$ is frequency and $\displaystyle \lambda $ is wavelength of EM waves, then

  1. $\displaystyle c=\nu\lambda $

  2. $\displaystyle \frac { \lambda }{ \nu } =c$

  3. $\displaystyle \frac { \nu }{ \lambda } =c$

  4. $\displaystyle \frac { 1 }{ \lambda } =\frac { c }{ \nu} $
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$\displaystyle c=\nu \lambda $
$c=$speed
$\nu=$Frequency
$\displaystyle \lambda $ = wavelength

Multiple choice electromagnetic spectrum electromagnetic waves physics

The broad wavelength range of visible spectrum is:

  1. $4000-8000A^o$

  2. $2000-4000A^o$

  3. $10000-20000A^o$

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The wavelength range of $4000-8000 A^o$ is known as visible spectrum as waves within this wavelength range create a sensation of vision in our eyes.

Multiple choice electromagnetic spectrum electromagnetic waves physics

Identify which of the following light rays has the highest energy?

  1. Violet

  2. Green

  3. Yellow

  4. Orange

  5. Red
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Energy of light ray      $E = h\nu$                $\implies E \propto \nu$

Among all the visible rays, violet ray has the highest frequency, Thus violet ray has the highest energy. 

Multiple choice electromagnetic spectrum electromagnetic waves physics

The portion of the spectrum beyond the red end is called

  1. UV spectrum

  2. Infrard spectrum

  3. Microwave

  4. All
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The portion of spectrum just beyond the red end is called infrared spectrum, while the portion of the spectrum just before the voilet end is called the ultravoilet spectrum.

Multiple choice electromagnetic spectrum electromagnetic waves physics

Wavelength of gamma rays are :

  1. ${ 10 }^{ -10 }m$ to less than ${ 10 }^{ -14 }m$

  2. ${ 10 }^{ -14 }m$ to less than ${ 10 }^{ -10 }m$

  3. ${ 10 }^{ -11 }m$ to less than ${ 10 }^{ -14 }m$

  4. ${ 10 }^{ -14 }m$ to less than ${ 10 }^{ -6 }m$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Electromagnetic radiations are present all around us in different forms such as microwaves, radio waves, gamma rays, and X-rays. These radiations can be defined as a form of energy produced by the movement of electrically charged particles that can be found in matter or vacuum or by oscillating magnetic or electric disturbance.


Properties of electromagnetic radiations :

1) They travel through empty space
2) The speed of light always remains constant i.e. 2.99792458 X 10 8 m/s.
3) Wavelength is the measure between the distance of either troughs or crests.  Its symbol is 'Lambda'.

Gamma rays have no mass.  They arise from the high-frequency end of the electromagnetic spectrum.  They have the highest penetration power.   They are at least ionizing.  The Gamma rays carry a large amount of energy and can travel through the thick and thin material. Gamma rays have frequencies greater than about 1018 cycles per second or Hertz.  They have wavelengths of less than 100 picometer.  Gamma rays can kill living cells.  It is used to kill cancerous cells.   They can also kill bacteria.

Multiple choice electromagnetic spectrum electromagnetic waves physics

Electromagnetic wave with frequencies greater than the critical frequency of ionosphere cannot be used for communication using sky wave propagation because

  1. The refractive index of ionosphere becomes very high for $f > f _ { c }$

  2. The refractive index of ionosphere becomes very low for $f > f _ { c }$

  3. The refractive index of ionosphere becomes very high for $f < f _ { c }$

  4. The refractive index of ionosphere becomes very low for $f < f _ { c }$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The refractive index of the ionosphere is given by n = sqrt(1 - (f_c/f)^2). For f > f_c, the refractive index is real and less than 1, but as f increases, the ionosphere becomes less effective at refracting the wave back to Earth, eventually allowing it to pass through.