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Blababa [14]
3 years ago
8

A sinusoidal electromagnetic wave in a vacuum is propagating in the positive z-direction. At a certain point in the wave at a ce

rtain instant in time, the electric field points in the negative x-direction. At the same point and at the same instant, the magnetic field points in the
A. positive y-direction.
B. negative y-direction.
C. positive z-direction.
D. negative z-direction.
E. none of the above
Physics
1 answer:
Sunny_sXe [5.5K]3 years ago
4 0

Answer:

The correct answer is B negative y-direction

Explanation:

An electromagnetic wave is created by the fluctuation of the electric and magnetic fields, which are perpendicular to each other, the direction of propagation is perpendicular to these two fields.

Let's apply the above to our problem, the wave propagates in the positive direction of the z-axis so that the electric and magnetic fields must be in the xy plane

They express that the electric field is in the negative direction of the x-axis, for the direction of the other field, we can make the vectoial product E x B with the result must be in positive z the only way is that the magnetic field (B) is in the negative direction of the y axis

The correct answer is B negative y-direction

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The kinetic energy of a proton and that of an a-particle are 4 eV and 1 eV,
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Answer:

  • <u><em>(b) 1:1</em></u>

Explanation:

<u></u>

<u>1. Formulae:</u>

  • E = hf  
  • E = h.v/λ
  • λ = h/(mv)
  • E = (1/2)mv²

Where:

  • E = kinetic energy of the particle
  • λ = de-Broglie wavelength
  • m = mass of the particle
  • v = speed of the particle
  • h = Planck constant

<u><em>2. Reasoning</em></u>

An alha particle contains 2 neutrons and 2 protons, thus its mass number is 4.

A proton has mass number 1.

Thus, the relative masses of an alpha particle and a proton are:

       \dfrac{m_\alpha}{m_p}=4

For the kinetic energies you find:

          \dfrac{E_\alpha}{E_p}=\dfrac{m_\alpha \times v_\alpha^2}{m_p\times v_p^2}

            \dfrac{1eV}{4eV}=\dfrac{4\times v_\alpha^2}{1\times v_p^2}\\\\\\\dfrac{v_p^2}{v_\alpha^2}=16\\\\\\\dfrac{v_p}{v_\alpha}=4

Thus:

           \dfrac{m_\alpha}{m_p}=4=\dfrac{v_p}{v__\alpha}

          m_\alpha v_\alpha=m_pv_p

From de-Broglie equation, λ = h/(mv)  

       \dfrac{\lambda_p}{\lambda_\alpha}=\dfrac{m_\lambda v_\lambda}{m_pv_p}=\dfrac{1}{1}=1:1

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V = 41.72m/s

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Explanation:

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Locomotive is pulling the train upwards ,

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