Since you are looking for the speed, you need to rearrange the formula which is f = speed / wavelength. That should give you speed = f (wavelength.) All you need to do next is to substitute the value to the following equation. speed = 250 Hz (6.0m) that should leave you with 1500 m/s which is very fast.
B because all you do is divide 16 and 8 to find your answer
With the use of the formula SinФ = nλ / d, there are 16 spectral orders which can be seen when it is illuminated by white light.
Given that a grating has 2000 slits/cm. That is,
d = 0.01 / 2000
d = 5 x
m
The wavelength λ = (700 - 400) nm
λ = 300 x
m
To calculate how many full spectral orders that can be seen (400 to 700 nm) when it is illuminated by white light, we will use the below formula
SinФ = nλ / d
Φ =
(nλ / d)
When n = 1
Φ =
(300 x
/ 5 x
)
Φ = 3.4 degrees
when n = 2
Φ =
(2 x 300 x
/ 5 x
)
Ф = 6.9 degrees
When n = 3
Ф =
(3 x 300 x
/ 5 x
)
When n = 16
Ф =
(16 x 300 x
/ 5 x
)
Ф =
(0.96)
Ф = 73.7 degrees
when n = 17
Ф =
(17 x 300 x
/ 5 x
)
Ф =
(1.05)
Ф = Error ( that is, it does not exist)
Therefore, there are 16 spectral orders which can be seen when it is illuminated by white light.
Learn more about double slit here: brainly.com/question/4449144
- The length of its image =

Given,
length of object, 
We know, for flat refracting surface,
Image distance = object distance
So,
magnification is = 
length of the image,

Here, negative sign means inverted image.
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