Engineers who design battery-operated devices such as cell phones and MP3 players try to make them as efficient as possible. An
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Answer:
The observer sees the space-probe 9.055m long.
Explanation:
Let be the length of the space-probe when measured at rest, and
be its length as observed by an observer moving at velocity
, then
Now, we know that and
, and putting these into
we get:
Thus, an observer moving at 0.95c observes the space-probe to be 9.055m long.
Answer:
The number of photons of light produced by the laser in 1 hour is
1 Photon / hour
Explanation:
Number of photons of light produced is given by
From the question,
Power = 5 mW (milliwatts) = 5 × 10⁻³ W
Since 1 Watt = 1 Js⁻¹
Then, 5 × 10⁻³ W = 5 × 10⁻³ Js⁻¹
For the Energy,
As given from the question
Energy=(Power)x(time)
Time = 1 hour = (1 × 60 × 60) s = 3600 s
∴ Energy = 5 × 10⁻³ Js⁻¹ x 1 x 3600s
Energy =18.0 J
Now for the Number of photons produced,
Power = 5 × 10⁻³ Js⁻¹ = 0.005 Js⁻¹
Number of photons = 2.78 × 10⁻⁴ Photons / sec
This is the number of photons produced in 1 second.
For the number of photons produced in 1 hour, we will multiply the result by 3600
(NOTE: 1 sec = hour)
Number of photons = 2.78 × 10⁻⁴ Photons / sec
= 2.78 × 10⁻⁴ × 3600 Photons / hour
= 1.0008 Photons / hour
≅ 1 Photon / hour
Hence, the number of photons of light produced by the laser in 1 hour is
1 Photon / hour