A surface receiving sound is moved from its original position to a position three times farther away from the source of the soun
1 answer:
Answer:
c. nine times as low.
Explanation:
Sound intensity is defined as the acoustic power transferred by a sound wave per unit of normal area to the direction of propagation:
Since the sound wave has a spherical wavefront of radius r, then the area is given by:
Here r is the distance from the source of the sound. Thus sound intensity decreases as:
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Answer:
Ф = 2.179 eV
Explanation:
This exercise has electrons ejected from a metal, which is why it is an exercise on the photoelectric effect, which is explained assuming the existence of energy quanta called photons that behave like particles.
E = K + Ф
the energy of the photons is given by the Planck relation
E = h f
we substitute
h f = K + Ф
Ф= hf - K
the speed of light is related to wavelength and frequency
c = λ f
f = c /λ
Φ =
let's reduce the energy to the SI system
K = 0.890 eV (1.6 10⁻¹⁹ J / 1eV) = 1.424 10⁻¹⁹ J
calculate
Ф = 6.63 10⁻³⁴ 3 10⁸/405 10⁻⁹ -1.424 10⁻¹⁹
Ф = 4.911 10⁻¹⁹ - 1.424 10⁻¹⁹
Ф = 3.4571 10⁻¹⁹ J
we reduce to eV
Ф = 3.4871 10⁻¹⁹ J (1 eV / 1.6 10⁻¹⁹ J)
Ф = 2.179 eV
Answer:
B = 7.6 T direction of + x
Explanation:
For the proton beam to continue in the same direction the electric and magnetic forces must be equal
= 0
= F_{e}
Fm = q E
The electric force is in the direction of the electric field because it is the charge of the positive proton, the electric force goes in the direction of –y, therefore, the magnetic force cancels this force must go in the direction of + y
The magnetic force is
F_{m} = q v x B = q v B sin θ
θ = 90
B = q E / q v
B = E / v
B = 800/105
B = 7.6 T
To find the direction of the magnetic field we use the right hand rule, the thumb goes in the direction of the proton velocity, the fingers extended in the direction of the magnetic field and the palm is the direction of force, for a positive charge.
Thumb goes in the direction of the + z axis
Palm in the direction of +y
Fingers point in the direction of + x