physics conceptual questions exam 4

1. What produces electromagnetic waves?

Accelerating electric charges or changing electric currents.

2. Are electromagnetic waves transverse or longitudinal?

Transverse.

3. Can electromagnetic waves travel through a vacuum?

Yes, they do not require a medium.

4. How are the electric and magnetic fields oriented in an electromagnetic wave?

They are perpendicular to each other and to the direction of wave propagation.

5. What is the speed of electromagnetic waves in a vacuum?

3.00 × 10^8 m/s.

6. What happens when a magnetic field changes with time?

It induces an electric field.

7. What happens when an electric field changes with time?

It produces a magnetic field.

8. Can a stationary electric charge produce electromagnetic radiation?

No, electromagnetic radiation generally requires an accelerating charge.

9. What does Gauss's law for magnetism state?

Magnetic field lines are continuous and have no beginning or end.

10. What happens to wavelength when frequency increases?

Wavelength decreases.

11. Which electromagnetic waves have the highest frequency and shortest wavelength?

Gamma rays.

12. Which electromagnetic waves have the lowest frequency and longest wavelength?

Radio waves.

13. What is the correct order of the electromagnetic spectrum from lowest to highest frequency?

Radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays.

14. Which visible color has the highest frequency and shortest wavelength?

Violet.

15. Which visible color has the lowest frequency and longest wavelength?

Red.

16. Which has more energy per photon, high-frequency or low-frequency electromagnetic radiation?

High-frequency radiation.

17. What is the main difference between sound waves and radio waves?

Sound requires a medium; radio waves can travel through a vacuum.

18. What happens to intensity when electric field amplitude doubles?

Intensity increases by a factor of four.

19. What is the relationship between peak intensity and average intensity for a sinusoidal electromagnetic wave?

Peak intensity is twice the average intensity.

20. If the power of a wave doubles while the area remains constant, what happens to intensity?

Intensity doubles.

21. What is the law of reflection?

The angle of incidence equals the angle of reflection.

22. Relative to what are angles of incidence and reflection measured?

The normal, perpendicular to the surface.

23. What is the difference between specular and diffuse reflection?

Specular reflection occurs on smooth surfaces; diffuse reflection occurs on rough surfaces.

24. What type of image does a plane mirror produce?

Virtual, upright, and the same size as the object.

25. Where is an image located in a plane mirror?

The same distance behind the mirror as the object is in front.

26. If you move away from a plane mirror at 2 m/s, how fast does your image move away from you?

4 m/s.

27. What is a virtual image?

An image where light rays appear to originate but do not actually converge.

28. What is a real image?

An image formed where actual light rays converge.

29. What is refraction?

The change in direction of light when it passes between materials with different refractive indices at an angle.

30. What causes refraction?

A change in the speed of light between materials.

31. What does a higher index of refraction indicate?

Light travels more slowly in the material.

32. What happens when light travels from a lower to a higher refractive index?

It slows down and bends toward the normal, except at normal incidence.

33. What happens when light travels from a higher to a lower refractive index?

It speeds up and bends away from the normal, except at normal incidence.

34. Light passes from air into water. Does it bend toward or away from the normal?

Toward the normal.

35. Light passes from water into air. Does it bend toward or away from the normal?

Away from the normal.

36. What happens when light enters a different medium perpendicular to the surface?

It continues straight without bending.

37. Does the frequency of light change when it enters a different medium?

No, frequency remains constant.

38. What happens to the wavelength of light when it enters a medium where it travels more slowly?

Wavelength decreases.

39. What is the critical angle?

The angle of incidence that produces an angle of refraction of 90°.

40. What two conditions are necessary for total internal reflection?

Light must travel from higher to lower refractive index, and the incident angle must exceed the critical angle.

41. What happens when the incident angle exceeds the critical angle?

Total internal reflection occurs.

42. Can total internal reflection occur when light travels from air into glass?

No.

43. Can total internal reflection occur when light travels from glass into air?

Yes, if the incident angle exceeds the critical angle.

44. What causes dispersion of white light in a prism?

Different wavelengths refract by different amounts.

45. Which color bends the most in an ordinary glass prism?

Violet.

46. Which color bends the least in an ordinary glass prism?

Red.

47. What causes a rainbow?

Refraction, dispersion, and internal reflection of sunlight in water droplets.

48. What is the difference between converging and diverging lenses?

Converging lenses bring parallel rays together; diverging lenses spread them apart.

49. What type of image does a diverging lens always produce for a real object?

Virtual, upright, and smaller.

50. What happens when an object is placed beyond 2F of a converging lens?

The image is real, inverted, and smaller.

51. What happens when an object is placed between F and 2F of a converging lens?

The image is real, inverted, and larger.

52. What happens when an object is placed inside the focal length of a converging lens?

The image is virtual, upright, and larger.

53. What happens when an object is placed at the focal point of a converging lens?

The outgoing rays are parallel and no finite image forms.

54. What type of image does a convex mirror always produce for a real object?

Virtual, upright, and smaller.

55. What type of image does a concave mirror produce when the object is inside the focal length?

Virtual, upright, and enlarged.

56. What type of image does a concave mirror produce when the object is beyond the center of curvature?

Real, inverted, and smaller.

57. Which mirror provides a wider field of view and is commonly used for security?

Convex mirror.

58. What does negative magnification indicate?

The image is inverted.

59. What does positive magnification indicate?

The image is upright.

60. What is the relationship between focal length and radius of curvature for a spherical mirror?

The focal length is half the radius of curvature in magnitude: f = R/2.