The correct answer is D. Correction for dip is always negative.
Refraction is the bending of light as it passes from one medium to another. When light passes from the air into the water, it bends towards the normal. This is because the speed of light is slower in water than in air. The amount of refraction depends on the angle of incidence, which is the angle between the incoming light ray and the normal. The greater the angle of incidence, the greater the amount of refraction.
Parallax is the apparent displacement of an object due to a change in the observer’s position. When
you look at an object from two different positions, the object appears to move in relation to the background. This is because the object is actually in a different position relative to the background from each of your two positions. The amount of parallax depends on the distance to the object and the difference in the observer’s positions.Semi-diameter is half the diameter of an object. The semi-diameter of the moon is about 3,474 kilometers. The semi-diameter of the sun is about 1,392,000 kilometers.
Dip is the apparent lowering of an object due to the curvature of the Earth. When you look at an object that is far away, the object appears to be lower than it actually is. This is because the Earth is curved, and the light from the object has to travel further to reach your eyes. The amount of dip depends on the distance to the object and the observer’s height above sea level.
In conclusion, the correction for dip is always negative because the object appears to be lower than it actually is.