A) lithium and beryllium
Explanation:
From the given row on the periodic table, only lithium and beryllium will conduct electricity.
What makes a substance able to conduct electricity?
- The presence of free mobile electrons and in some, ions allows them to carry electric currents.
Metals are generally known to be good conductors of heat and electricity. This is because, metals have a large pool of electrons i.e free mobile electrons. They are electropositive with a large size and readily release their electrons for conduction.
Lithium and Beryllium are in the metallic block on the periodic table.
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Answer:
4
Explanation:
We know that intensity I = P/A where P = power and A = area through which the power passes through.
Now, let the initial intensity of the speaker be I₀ and its initial power be P₀. Since the intensity is increased by a factor of 4, the new intensity be I and new power be P.
So, I = P/A and I₀ = P₀/A
Now, if I = 4I₀,
P/A = 4P₀/A
P = 4P₀
Now, energy E = Pt, where t = time. So, P = E/t and P₀ = E₀/t
Substituting P and P₀ into the equation, we have
P = 4P₀
E/t = 4E₀/t
E = 4E₀
Since the energy is four times the initial energy, the energy output increases by a factor of 4.
Answer:
phase difference = π / 2
constructive interference
Explanation:
Given data
wavelength = 420 nm
1st beam = 105 nm
path difference = 105 nm
to find out
phase difference and interference pattern of the two beams
solution
we use here equation of phase difference that is
phase difference = 2π / wavelength × Δx
put here value
phase difference = 2π / 420 × 105
phase difference = π / 2
and
we know that here path difference Δx is the integral multiple of the wavelength so it will be constructive interference
Δx is wavelength / 4
