Answer: f = -12 cm
Explanation: <u>Combined</u> <u>lenses</u> is an array of simple lenses with a common axis. The combination is useful for correction of optical aberrations which cannot be corrected by simple lenses.
When two lenses are in contact and are thin, focal lengths are related as:

If there is a distance between the lenses, the focal length will be:

Since the lenses in the question above are thin and in contact, the focal length of one of them will be:




-12
The focal length of the other lens is -12 cm, with the negative sign meaning it's a converging lens.
Answer + Explanation:
B
She can measure the volume and mass of the marble, the volume and mass of the water, and the mass of the graduated cylinder.
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Answer:
the magnitude of the angular magnification of the telescope. is 4
Explanation:
Calculate the magnitude of the angular magnification of the telescope.
Given that,
distance = 25cm
focal length from the objective f₀ = 20cm
focal length from eye piece f₁ = 5cm
The angular magnification of the telescope is

Magnification = 20 / 5
magnification = 4
Hence, the magnitude of the angular magnification of the telescope. is 4
<u>Metal detectors work by transmitting an electromagnetic field from the search coil into the ground. Any metal objects (targets) within the electromagnetic field will become energised and retransmit an electromagnetic field of their own. The detector’s search coil receives the retransmitted field and alerts the user by producing a target response. metal detectors are capable of discriminating between different target types and can be set to ignore unwanted targets.
</u>
1. Search Coil
The detector’s search coil transmits the electromagnetic field into the ground and receives the return electromagnetic field from a target.
2. Transmit Electromagnetic Field (visual representation only - blue)
The transmit electromagnetic field energises targets to enable them to be detected.
3. Target
A target is any metal object that can be detected by a metal detector. In this example, the detected target is treasure, which is a good (accepted) target.
<em>hope this helps PLEASE MARK AS BRAINLIEST:)</em>
When ignited, the gas mixture converts to water vapor and releases energy, which sustains the reaction: 241.8 kJ of energy (LHV) for every mole of H2 burned.” A mole of hydrogen weighs 2 grams. So, this is a LHV (lower heating value) of 120.9 kJ/gram of hydrogen when heat of vaporization is subtracted.