it is very normal. It is not necessary that they suspect something but may be they do.
It took 8 weeks may be because it is the summer time and the embassy receives many applications for touristic and study visas.
My advice is that you have to sit with your wife on Skype and go over all the possible questions (see below). Make sure she knows ALL YOUR LIFE DETAILS in Canada. Also, if you have any additional documents or information that was not submitted with the original file, please send them now. I assume your file is in Ottawa. Write a cover letter with your file number and send them to Ottawa. You can also send them to your wife (if they requested that she brings further documentation with her but I assume they did not because the file is processed in Ottawa and giving the documents to Cairo would be useless). Because your file is processed in Ottawa, the visa officer who reviewed it in Ottawa is different from the one who will do the interview in Cairo. There might be something in the mind of the Ottawa officer and deliver it to the Cairo officer to ask your spouse about them (just guessing). Some people try to get the system notes (called CAIPS, I think) to see the concerns of the officer. If you have time to get the CAIPS records, do it.
I copied and pasted all kinds of questions. Go over them with your wife..you have enough time to finish them all and repeat them several times. Insh'allah things will be fine.
Types of interview questions generally VO asks the applicant :-
1. When and where did you meet your spouse for the first time?
2. How did you meet your spouse?
3. How old is your spouse? What is your spouse's birth date?
4. What does your spouse do for a living?
5. Where did your spouse go to school'?
6. What degrees or formal training does your spouse have?
7. How did your spouse immigrate to Canada?
8. Where does your spouse work?
9. What is the name of the company? What position does your spouse hold? How long has your spouse worked there?
10. What does the job entail?
1l. Does your spouse like his or her job?
12. What is the salary?
13. Where does your spouse live?
14. Whom does your spouse live with?
15. Where are you going to live when you go to Canada?
16. Please explain the type of relationship you have had since your first meeting.
17. What is your religion?
18. What is the religion of your spouse?
19. Do you have any hobbies? Describe them.
20. Does your spouse have any hobbies? Describe them.
21. What type of music do you enjoy?
22. What type of music does your spouse enjoy?
23. What kind of movies do you enjoy?
24. What kind of movies does your spouse enjoy?
25. What kind of books do you read?
26. What kind of books does your spouse read?
27. Have you and your spouse ever exchanged gifts? Explain.
28. When and where did the marriage proposal take place?
29. Was your marriage arranged?
30. If it was arranged describe how it was arranged and by whom?
31. Did you have a ceremony celebrating your relationship?
32. Where was it held?
33. When was it held?
34. Describe the ceremony?
35. Did it conform to your own religious and cultural beliefs? Explain.
36. When did you get married?
37. Where did you get married?
38. Who was at the wedding?
39. What family members were there?
40. How many people were at the ceremony?
41. What day was the ceremony held on?
42. Who performed the ceremony?
43. Do you have pictures of the ceremony?
44. Who was at the ceremony from your side?
45. Who was at the ceremony from your spouses side?
46. Were any friends present?
47. How many brothers and sisters does your spouse have?
48. Were your parents at the wedding? If not, why not?
49. Are your parents aware of the wedding? If not, why not?
50. Where your spouses parents at the wedding? If not, why not?
51. Were your spouses parents aware of the wedding? If not, why not?
52. Was a reception held? When and where was it held?
53. Who was present at the reception?
54. Did you receive any wedding gifts? Describe them.
55. Did you on a honeymoon? Where did you go and for how long?
56. Can you show me pictures and receipts from the honeymoon, wedding and reception?
57. Have you or your spouse been married before?
58. Why was that relationship dissolved?
59. Do you have any children from your current relationship or marriage?
60. How many children?
61. What are the names and birth dates?
62. Where are the children now?
63. Who looks after the children?
64. Do any other family members reside with you and your spouse? If yes, please indicate their names and relationship.
65. What relatives do you have in Canada?
66. What are their names and where do they live?
67. What relatives do you have outside of Canada?
68. Has your spouse met any of your relatives or friends? Who have they met and when did they meet them?
69. Have you met any of your spouses relatives or friends? Whom have you met and when did you meet them?
70. In terms of education, would you say that you and your spouses educational background are compatible?
71. What will you do when you go to Canada'?
72. Why did you marry your spouse?
73. Since your marriage have you seen your spouse? If not, why not?
74. Do your family members (parents, siblings) want to immigrate to Canada?
75. Did you marry your spouse so that you could sponsor your parents as landed immigrants of Canada?
76. How do you correspond with your spouse?
77. How often do you talk on the phone?
78. Do you have phone bills, e-mails, cards, etc., and can I see them?
79. Tell me why this marriage or relationship is genuine.
80. What makes your relationship with your spouse different from that of a female/male friend?
81. Does your spouse support you financially?
82. Do you support your spouse financially?
83. If I refuse this application what will you do?
84.When you and your spouse were dating what would you do together? GOOD LUCK
Regards and wishes,