Answer:
Apparent
The key discovery about Cepheid variable stars that led in the 1920s to the resolution of the question of whether spiral "nebulae" were separate and distant galaxies or part of the Milky Way Galaxy was the direct relationship between the pulsation period and the absolute brightness or luminosity of the Cepheid variables. A measurement of apparent brightness of a variable star could then be used to determine the distance to the "nebula" containing it.
Explanation:
A variable star is a star with changing apparent brightness. The changes can occur over years or in a fraction of seconds. For example the sun whose energy output varies by approximately 0.1 percent of its magnitude, over an 11-year solar cycle. This variable(apparent brightness) can be used to determine how far a variable star is (distance). Therefore, a measurement of apparent brightness of a variable star could then be used to determine the distance to the "nebula" containing it.
Answer:
Explanation: This is a type of radioactive decay and all the radioactive process follow first order kinetics.
Half life is the time required to decompose half of the reactants. thus after every half life the reactant will decompose to half of its present value.
Now, to calculate the number of half lives, we use the formula:
where,
a = amount of reactant left after n-half lives = ?
=Let Initial amount of the reactant = 100 g
n = number of half lives
Answer:
θ = 61.3°
She must swim at an angle of 61.3°
Explanation:
Given;
Width of river = 100 m
Alicia speed in still water = 2.5m/s
Current of river = 1.2m/s
The angle for her to achieve her goal can be derived by the summation of velocity in the direction of the current.
Her speed in the opposite direction of the current must be able to neutralise the speed of the current;
2.5cosθ - 1.2 = 0
2.5cosθ = 1.2
cosθ = 1.2/2.5
θ = cosinverse(1.2/2.5)
θ = 61.3°
Answer:
The cross-sectional area is
Explanation:
From the question we are told that
The dimension of the cell is 6.9 × 10-4 cm by 1.1 × 10-3 cm =
Generally the cross-sectional area is mathematically represented as
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