P7 - Further Physics Flashcards
How is the position of stars relative to a fixed point on the equator measured?
Using the angles of declination and right ascension
What directions are right ascension and declination?
Right ascension -> east - west
Declination -> north - south
What are the units of right ascension?
Degrees and minutes (1 hour = 15 degrees)
How long is the moon’s orbit of earth?
28 days
Why can we see the moon at night?
It reflects the sun’s light
In terms of eclipses, what happens during the waxing phases?
The lit area of the moon gets bigger
In terms of eclipses, what happens during the waning phases?
The lit area of the moon gets smaller
Name the 8 phases of the moon in order
HINT start with the new moon
- New moon
- Waxing crescent
- First quarter
- Waxing gibbous
- Full moon
- Waning gibbous
- Last quarter
- Waning crescent
How does a solar eclipse occur?
A solar eclipse occurs when the moon passes between the earth and the sun and casts a shadow on the earth.
How does a lunar eclipse occur?
A lunar eclipse occurs when the earth is between the sun and moon and casts a shadow on the moon.
Why don’t eclipses occur monthly? (2)
- The moon’s orbit is inclined at a 5 degree angle above Earth so its shadow is usually above or below earth also the full moon isn’t always in earth’s shadow
- Eclipses can only occur when the moon passes through the ecliptic
How long is a solar day?
24 hours
What happens to waves when they are refracted?
The frequency remains the same but the wavelength changes and so does the wave speed
What is the formula for wave speed/ velocity?
Velocity = Frequency x Wavelength
What happens to waves when they are diffracted?
They spread out at the edges
When is diffraction most obvious? (2)
- when the size of the gap is similar to or smaller than the wavelength
- when the waves that pass an object have a wavelength larger than the object
Give the other name for convex lenses
Converging lenses
What do convex lenses do?
They refract rays of parallel light towards a focal point
The image made at the focus of a convex lens is… (3)
- Inverted (upside down)
- Smaller than the original image
- A Real image
The … the curvature of a lens the … its power
The greater the curvature the greater its power
The formula to work out the power of a lens is? Include units
Power (Dioptres) = 1 / the focal length (metres)
What are the two lenses used in a refractor telescope and how powerful are they in relation to each other? (3)
Two converging lenses of different power are used, one is the objective lens and the other is the eyepiece lens. The eyepiece lens has the greater of the two.
How do refractor telescopes work? (2)
- the objective lens captures parallel light and brings it to a focal point
- this point is also the focal point of the eyepiece lens so the image acts as the object of that lens and is magnified
How is angular magnification calculated?
Angular magnification = Focal length of objective lens / focal length of eyepiece lens