Snells Law - Problem understanding question

[maybnxtseasn]

I have no idea what angle it's talking about and also what angle I am supposed to get in this problem. It seems to me like the problem is written wrong. Could anyone please let me know if it is wrong or right. If it's a valid problem could you also post a simple MSPaint drawing of how this should be drawn with the 30degree angle along with the angle I am supposed to find :) thanks!



One of the contests at the school carnival is to throw a spear at an underwater target lying flat on the bottom of a pool. The water is 1.20m deep. You're standing on a small stool that places your eyes 3.10m above the bottom of the pool. As you look at the target, your gaze is 30degrees below horizontal. At what angle below horizontal should you throw the spear in order to hit the target?

 

[Emilyjoint]

were you given the refractive index of the water in the pool or were you asked to find it.

 

[jbriggs444]

The problem seems well-posed to me.

Water has a known refractive index.

If you know the angle of incidence, you can calculate the angle to which the line of sight is refracted below the water. That's Snell's Law.

We are told that the line of sight above the water is 30 degrees from the horizontal. That means that it is 60 degrees from the vertical.

Given the refracted angle and the known depth of the pool you can calculate the point of intersection of the line of sight with the bottom of the pool.

Then it's just a matter of aiming your spear at that point.

 

[HallsofIvy]

I have no idea what angle it's talking about and also what angle I am supposed to get in this problem. It seems to me like the problem is written wrong. Could anyone please let me know if it is wrong or right. If it's a valid problem could you also post a simple MSPaint drawing of how this should be drawn with the 30degree angle along with the angle I am supposed to find :) thanks!



One of the contests at the school carnival is to throw a spear at an underwater target lying flat on the bottom of a pool. The water is 1.20m deep. You're standing on a small stool that places your eyes 3.10m above the bottom of the pool. As you look at the target,

your gaze is 30degrees below horizontal

Draw horizontal line from your eyes. Your gaze is 30 degrees below that. By the 'alternate angles theorem' for parallel lines, your line of sight also makes a 30 degree angle with the surface of the water.

. At what angle below horizontal should you throw the spear in order to hit the target?

 

[sardar]

Hello,

It seems like you are having trouble understanding the problem and the concept of Snell's Law. Snell's Law is a principle in physics that describes the relationship between the angle of incidence and the angle of refraction when a light ray passes through a boundary between two different mediums, such as air and water.

In this problem, the angle being referred to is the angle of incidence, which is the angle at which the spear will enter the water. The angle you are supposed to find is the angle of refraction, which is the angle at which the spear will change direction and travel towards the target at the bottom of the pool.

To help you visualize the problem, imagine a straight line from your eyes to the target on the bottom of the pool. This line forms an angle of 30 degrees below horizontal. Now, when the spear enters the water, it will bend or refract due to the change in medium. The angle of refraction will depend on the angle of incidence and the refractive index of water.

To find the angle of refraction, you can use the formula for Snell's Law: n1sinθ1 = n2sinθ2, where n1 and n2 are the refractive indices of air and water, respectively, and θ1 and θ2 are the angles of incidence and refraction.

I have attached a simple MSPaint drawing to help you visualize the problem better. I hope this helps you understand the problem better. If you still have any doubts, please feel free to ask for clarification.

Best regards,