convolutional neural network grayscale image in keras

# Three steps to create a CNN
# 1. Convolution
# 2. Activation
# 3. Pooling
# Repeat Steps 1,2,3 for adding more hidden layers

# 4. After that make a fully connected network
# This fully connected network gives ability to the CNN
# to classify the samples

model = Sequential()

model.add(Conv2D(32, (3, 3), input_shape=(28,28,1)))
model.add(BatchNormalization(axis=-1))
model.add(Activation('relu'))
model.add(Conv2D(32, (3, 3)))
model.add(BatchNormalization(axis=-1))
model.add(Activation('relu'))
model.add(MaxPooling2D(pool_size=(2,2)))

model.add(Conv2D(64,(3, 3)))
model.add(BatchNormalization(axis=-1))
model.add(Activation('relu'))
model.add(Conv2D(64, (3, 3)))
model.add(BatchNormalization(axis=-1))
model.add(Activation('relu'))
model.add(MaxPooling2D(pool_size=(2,2)))

model.add(Flatten())

# Fully connected layer
model.add(Dense(512))
model.add(BatchNormalization())
model.add(Activation('relu'))
model.add(Dropout(0.2))
model.add(Dense(10))

model.add(Activation('softmax'))