Refraction of Light question assistance needed

[Issy]

As revision for my upcoming physics exam, I'm doing an old exam paper from a previous year of the course, for which the answers aren't published. However, I'm stuck on a basic angle of refraction question:
"A light ray makes an angle of 35degrees to the surface of an oil layer. [A diagram is attached, which shows the light ray traveling through air until it hits the oil surface]. The air's n=1.00, and the oil''s n=1.47. What is the angle of refraction of the light ray in the oil?"

It's a multichoice answer, and the answers are A) 35degrees, B) 56.1degrees, C) 55.9degrees, D) 33.9degrees, and E) 67.7.
However when I use the n1*sin(theta1) = n2*sin(theta2) method, my answer is always equal to 22.97degrees? Which is equal to none of the multichoice answer values? And because there are no published answers, I can't check the correct answer.
Have I done something wrong? Or is there a mistake in the exam paper? Thank you for any and all help!
[P.S. my calculator is definitely set in degrees.]

Relevant equations:
n1*sin(theta1) = n2*sin(theta2)

The attempt at a solution:
1 * sin(35) = 1.47 * sin(theta2), therefore sin^-1 (sin(35)/1.47) = theta2 = 22.97degrees.

 

[andrevdh]

Try 90^o - 35^o as the incident angle.
The incident angle for Snell's law is measured with respect to the normal to the surface.

 

[Issy]

Try 90^o - 35^o as the incident angle.
The incident angle for Snell's law is measured with respect to the normal to the surface.

Thank you very much! A dumb mistake on my part; you've saved me from embarrassing myself in front of my lecturer when I went to ask him for help, and the extra info at the bottom was also very helpful, thank you again!

 

[andrevdh]

Don't be afraid to make mistakes or ask questions (and hopefully do not break anything in the process). That is (mostly) how we learn.