Jake drove 160 kilometres in 2 hours. What was his speed, in kmh-1
2 answers:
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Answer:
The farther star will appear 4 times fainter than the star that is near to the observer.
Explanation:
Since it is given that the luminosity of the 2 stars is same thus they radiate the same energy per unit time
Consider a spherical wave front of energy 'E' that leaves both the stars (Both radiate 'E' as they have same luminosity)
This Energy is spread over the whole surface area of sphere Thus when the wave front is at a distance 'r' the energy per unit surface area is given by
For the star that is twice away from the earth the distance is '2r' thus we will receive an energy given by
Hence we sense it as 4 times fainter than the nearer star.
Answer:
140°
Explanation:
The law of reflection states that the angle of redlection equals to the angle of incidence.
When light rays hit surface at 20°, they also leave the surface at the same angle
Since the whole surface has 180° then subtracting these two angles from total angle gives the the angle between the incident and reflected rays.
180°-20°-20°=140°
The angle of incidence and reflection are equal hence 140/2=70°
The question needed the angle between the incident and reflected rays which is already calculated as 140°
Answer:
Explanation:
P = Acoustic power = 63 µW
r = Distance to the sound source = 210 m
Acoustic power
Threshold intensity =
Ratio
Ratio of the acoustic intensity produced by the juvenile howler to the reference intensity is 113.68