The answer is B hope this helps
(a) 
The frequency of a wave is given by:
where
v is the wave's speed
is the wavelength
For the red laser light in this problem, we have
(speed of light)
Substituting,
(b) 427.6 nm
The wavelength of the wave in the glass is given by
where
is the original wavelength of the wave in air
n = 1.48 is the refractive index of glass
Substituting into the formula,
(c) 
The speed of the wave in the glass is given by
where
is the original speed of the wave in air
n = 1.48 is the refractive index of glass
Substituting into the formula,
Answer:
see explanation
Explanation:
There is an increasing demand for materials and natural resources from a growing global population, especially those in more economically developed countries. The world's resources are being used up more quickly. The consumption of resources is spread unequally between MEDCs (more economically developed countries), who use more resources, and LEDCs (less economically developed countries), who use less.
The gap between the rich and poor is more evident when the resources are shared so unevenly and unfairly and natural resources like materials and natural energy cannot reach the demand of the people which can have consequences and be very difficult to manage. Having a lack of these materials in a country can result in prices going up for them, and the industry could be harder to work in because of a lack of materials.
Answer: The correct explanation is 2.
Explanation: The warm air is less dense (it expands) and thus it is lighter than the cold air so it will rise up to the floor. Therefore, when you place the heater on the floor it will warm the cold air which would then rise and be replaced by more cold air which would again get warm and rise and so on until the room is heated. This means that the correct explanation is 2.
On the other hand, if you put the heater at the ceiling, it will warm the cold air near the ceiling which would stay up there (it is lighter than the cold air under it). This means that the only way for the heat to spread from this ceiling level warm air to the lower levels is via conduction which is slow.
